Data In H2O¶

Loading Data From A CSV File¶

H2O’s parser supports data of various formats from multiple sources. The following formats are supported:

• SVMLight
• CSV (data may delimited by any of the 128 ASCII characters)
• XLS

The following data sources are supported:

• NFS / Local File / List of Files
• HDFS
• URL
• A Directory (with many data files inside at the same level – no support for recursive import of data)
• S3/S3N
• Native Language Data Structure (c.f. the subsequent section)

>>> trainFrame = h2o.import_file(path="hdfs://192.168.1.10/user/data/data_test.csv")
#or
>>> trainFrame = h2o.import_file(path="~/data/data_test.csv")

Loading Data From A Python Object¶

To transfer the data that are stored in python data structures to H2O, use the H2OFrame constructor and the python_obj argument. If the python_obj argument is not None, then additional arguments are ignored.

The following types are permissible for python_obj:

• tuple ()
• list []
• dict {}
• collections.OrderedDict

The type of python_obj is inspected by performing an isinstance call. A ValueError will be raised if the type of python_obj is not one of the above types. For example, sets, byte arrays, and un-contained types are not permissible.

The subsequent sections discuss each data type in detail in terms of the “source” representation (the python object) and the “target” representation (the H2O object). Concretely, the topics of discussion will be on the following: Headers, Data Types, Number of Rows, Number of Columns, and Missing Values.

In the following documentation, H2OFrame and Frame will be used synonymously. Technically, an H2OFrame is the object-pointer that resides in the python VM and points to a Frame object inside of the H2O JVM. Similarly, H2OFrame, Frame, and H2O Frame all refer to the same kind of object. In general, though, the context is from the python VM, unless otherwise specified.

H2OFrame¶

class h2o.frame.H2OFrame(python_object=None)[source]¶

Bases: object

abs()[source]¶

acos()[source]¶

acosh()[source]¶

all()[source]¶

True if every element is True or NA in the column.

any()[source]¶

True if any element is True or NA in the column.

any_na_rm()[source]¶

True if any element is True in the column.

anyfactor()[source]¶

Test if H2OFrame has any factor columns.

True if there are any categorical columns; False otherwise.

apply(fun=None, axis=0)[source]¶

Apply a lambda expression to an H2OFrame.

fun: lambda

A lambda expression to be applied per row or per column

axis: int

0: apply to each column; 1: apply to each row

H2OFrame

as_data_frame(use_pandas=False)[source]¶

Obtain the dataset as a python-local object.

use_pandas : bool, default=False

A flag specifying whether or not to return a pandas DataFrame.

A local python object (a list of lists of strings, each list is a row, if use_pandas=False, otherwise a pandas DataFrame) containing this H2OFrame instance’s data.

as_date(format)[source]¶

Return the column with all elements converted to millis since the epoch.

format : str

A datetime format string (e.g. “YYYY-mm-dd”)

An H2OFrame instance.

ascharacter()[source]¶

All columns converted to String columns

H2OFrame

asfactor()[source]¶

H2Oframe of one column converted to a factor.

asin()[source]¶

asinh()[source]¶

asnumeric()[source]¶

All factor columns converted to numeric.

H2OFrame

atan()[source]¶

atanh()[source]¶

cbind(data)[source]¶

Append data to this H2OFrame column-wise.

data : H2OFrame

H2OFrame to be column bound to the right of this H2OFrame.

H2OFrame of the combined datasets.

ceil()[source]¶

col_names None[source]¶

A list of column names.

columns None[source]¶

A list of column names.

cos()[source]¶

cosh()[source]¶

cospi()[source]¶

countmatches(pattern)[source]¶

For each string in the column, count the occurrences of pattern.

pattern : str

The pattern to count matches on in each string.

A single-column H2OFrame containing the counts for the per-row occurrences of pattern in the input column.

cummax()[source]¶

The cumulative max over the column.

cummin()[source]¶

The cumulative min over the column.

cumprod()[source]¶

The cumulative product over the column.

cumsum()[source]¶

The cumulative sum over the column.

cut(breaks, labels=None, include_lowest=False, right=True, dig_lab=3)[source]¶

Cut a numeric vector into factor “buckets”. Similar to R’s cut method.

breaks : list

The cut points in the numeric vector (must span the range of the col.)

labels: list

Factor labels, defaults to set notation of intervals defined by breaks.

include_lowest : bool

By default, cuts are defined as (lo,hi]. If True, get [lo,hi].

right : bool

Include the high value: (lo,hi]. If False, get (lo,hi).

dig_lab: int

Number of digits following the decimal point to consider.

Single-column H2OFrame of categorical data.

day()[source]¶

Day column from a msec-since-Epoch column

dayOfWeek()[source]¶

Day-of-Week column from a msec-since-Epoch column

ddply(cols, fun)[source]¶

Unimplemented

describe()[source]¶

Generate an in-depth description of this H2OFrame. Everything in summary(), plus the data layout.

digamma()[source]¶

dim None[source]¶

The number of rows and columns in the H2OFrame as a list [rows, cols].

drop(i)[source]¶

Drop a column from the current H2OFrame.

i : str, int

The column to be dropped

H2OFrame with the column at index i dropped. Returns a new H2OFrame.

exp()[source]¶

expm1()[source]¶

filter_na_cols(frac=0.2)[source]¶

Filter columns with proportion of NAs >= frac.

frac : float

Fraction of NAs in the column.

A list of column indices

flatten()[source]¶

floor()[source]¶

frame_id None[source]¶

Get the name of this frame.

static from_python(python_obj, destination_frame='', header=(-1, 0, 1), separator='', column_names=None, column_types=None, na_strings=None)[source]¶

Properly handle native python data types. For a discussion of the rules and permissible data types please refer to the main documentation for H2OFrame.

python_obj : tuple, list, dict, collections.OrderedDict

If a nested list/tuple, then each nested collection is a column.

destination_frame : str, optional

The unique hex key assigned to the imported file. If none is given, a key will automatically be generated.

header : int, optional

-1 means the first line is data, 0 means guess, 1 means first line is header.

sep : str, optional

The field separator character. Values on each line of the file are separated by this character. If sep = “”, the parser will automatically detect the separator.

col_names : list, optional

A list of column names for the file.

col_types : list or dict, optional

A list of types or a dictionary of column names to types to specify whether columns should be forced to a certain type upon import parsing. If a list, the types for elements that are None will be guessed. The possible types a column may have are:

“unknown” - this will force the column to be parsed as all NA “uuid” - the values in the column must be true UUID or will be parsed as NA “string” - force the column to be parsed as a string “numeric” - force the column to be parsed as numeric. H2O will handle the

compression of the numeric data in the optimal manner.

“enum” - force the column to be parsed as a categorical column. “time” - force the column to be parsed as a time column. H2O will attempt to

parse the following list of date time formats.

date:

“yyyy-MM-dd” “yyyy MM dd” “dd-MMM-yy” “dd MMM yy”

time:

“HH:mm:ss” “HH:mm:ss:SSS” “HH:mm:ss:SSSnnnnnn” “HH.mm.ss” “HH.mm.ss.SSS” “HH.mm.ss.SSSnnnnnn”

Times can also contain “AM” or “PM”.

na_strings : list or dict, optional

A list of strings, or a list of lists of strings (one list per column), or a dictionary of column names to strings which are to be interpreted as missing values.

A new H2OFrame instance.

>>> l = [[1,2,3,4,5], [99,123,51233,321]]
>>> l = H2OFrame(l)
>>> l

gamma()[source]¶

static get_frame(frame_id)[source]¶

Create an H2OFrame mapped to an existing id in the cluster.

H2OFrame that points to a pre-existing big data H2OFrame in the cluster

group_by(by)[source]¶

Returns a new GroupBy object using this frame and the desired grouping columns.

The returned groups are sorted by the natural group-by column sort.

by : list

The columns to group on.

A new GroupBy object.

gsub(pattern, replacement, ignore_case=False)[source]¶

Globally substitute occurrences of pattern in a string with replacement.

pattern : str

A regular expression.

replacement : str

A replacement string.

ignore_case : bool

If True then pattern will match against upper and lower case.

H2OFrame

head(rows=10, cols=200)[source]¶

Analogous to Rs head call on a data.frame.

rows : int, default=10

Number of rows starting from the topmost

cols : int, default=200

Number of columns starting from the leftmost

An H2OFrame.

hist(breaks='Sturges', plot=True, **kwargs)[source]¶

Compute a histogram over a numeric column.

breaks: str, int, list

Can be one of “Sturges”, “Rice”, “sqrt”, “Doane”, “FD”, “Scott.” Can be a single number for the number of breaks. Can be a list containing sthe split points, e.g., [-50,213.2123,9324834] If breaks is “FD”, the MAD is used over the IQR in computing bin width.

plot : bool, default=True

If True, then a plot is generated

If plot is False, return H2OFrame with these columns: breaks, counts, mids_true, mids, and density; otherwise produce the plot.

hour()[source]¶

Hour-of-Day column from a msec-since-Epoch column

ifelse(yes, no)[source]¶

Equivalent to [y if t else n for t,y,n in zip(self,yes,no)]

Based on the booleans in the test vector, the output has the values of the yes and no vectors interleaved (or merged together). All Frames must have the same row count. Single column frames are broadened to match wider Frames. Scalars are allowed, and are also broadened to match wider frames.

test : H2OFrame (self)

Frame of values treated as booleans; may be a single column

yes : H2OFrame

Frame to use if [test] is true ; may be a scalar or single column

no : H2OFrame

Frame to use if [test] is false; may be a scalar or single column

H2OFrame of the merged yes/no Frames/scalars according to the test input frame.

impute(column, method='mean', combine_method='interpolate', by=None)[source]¶

Impute a column in this H2OFrame

column : int, str

The column to impute

method: str, default=”mean”

How to compute the imputation value.

combine_method: str, default=”interpolate”

For even samples and method=”median”, how to combine quantiles.

by : list

Columns to group-by for computing imputation value per groups of columns.

An H2OFrame with the desired column’s NAs filled with imputed values. Note that the returned Frame is in conceptually a new Frame, but due to back-end optimizations is frequently not actually a copy.

insert_missing_values(fraction=0.1, seed=None)[source]¶

Inserting Missing Values into an H2OFrame. This is primarily used for testing.

Randomly replaces a user-specified fraction of entries in a H2O dataset with missing values.

WARNING: This will modify the original dataset. Unless this is intended, this function should only be called on a subset of the original.

fraction : float

A number between 0 and 1 indicating the fraction of entries to replace with missing.

seed : int

A random number used to select which entries to replace with missing values.

H2OFrame with missing values inserted.

interaction(factors, pairwise, max_factors, min_occurrence, destination_frame=None)[source]¶

Categorical Interaction Feature Creation in H2O. Creates a frame in H2O with n-th order interaction features between categorical columns, as specified by the user.

factors : list

factors Factor columns (either indices or column names).

pairwise : bool

Whether to create pairwise interactions between factors (otherwise create one higher-order interaction). Only applicable if there are 3 or more factors.

max_factors: int

Max. number of factor levels in pair-wise interaction terms (if enforced, one extra catch-all factor will be made)

min_occurrence: int

Min. occurrence threshold for factor levels in pair-wise interaction terms

destination_frame: str, optional

A string indicating the destination key.

H2OFrame

is_src_in_self(src)[source]¶

ischaracter()[source]¶

True if the column is a character column, otherwise False (same as isstring)

isfactor()[source]¶

Test if the selection is a factor column. Returns ——-

True if the column is categorical; otherwise False. For String columns, the result is False.

isna()[source]¶

For each row in a column, determine if it is NA or not.

Single-column H2OFrame of 1s and 0s. 1 means the value was NA.

isnumeric()[source]¶

True if the column is numeric, otherwise return False

isstring()[source]¶

True if the column is a string column, otherwise False (same as ischaracter)

kfold_column(n_folds=3, seed=-1)[source]¶

Build a fold assignments column for cross-validation. This call will produce a column having the same data layout as the calling object.

n_folds : int

An integer specifying the number of validation sets to split the training data into.

seed : int, optional

Seed for random numbers as fold IDs are randomly assigned.

A single column H2OFrame with the fold assignments.

levels()[source]¶

Get the factor levels.

A dictionary of column_name:column_levels pairs.

lgamma()[source]¶

log()[source]¶

log10()[source]¶

log1p()[source]¶

log2()[source]¶

logical_negation()[source]¶

match(table, nomatch=0)[source]¶

Makes a vector of the positions of (first) matches of its first argument in its second.

Parameters:	table – nomatch –
Returns:	H2OFrame of one boolean column

max()[source]¶

The maximum value of all frame entries

mean(na_rm=False)[source]¶

Compute the mean.

na_rm: bool, default=False

If True, then remove NAs from the computation.

A list containing the mean for each column (NaN for non-numeric columns).

median(na_rm=False)[source]¶

Compute the median.

na_rm: bool, default=False

If True, then remove NAs from the computation.

A list containing the median for each column (NaN for non-numeric columns).

merge(other, allLeft=True, allRite=False)[source]¶

Merge two datasets based on common column names

other: H2OFrame

Other dataset to merge. Must have at least one column in common with self, and all columns in common are used as the merge key. If you want to use only a subset of the columns in common, rename the other columns so the columns are unique in the merged result.

allLeft: bool, default=True

If True, include all rows from the left/self frame

allRite: bool, default=True

If True, include all rows from the right/other frame

Original self frame enhanced with merged columns and rows

min()[source]¶

The minimum value of all frame entries

static mktime(year=1970, month=0, day=0, hour=0, minute=0, second=0, msec=0)[source]¶

All units are zero-based (including months and days). Missing year is 1970.

year : int, H2OFrame month: int, H2OFrame day : int, H2OFrame hour : int, H2OFrame minute : int, H2OFrame second : int, H2OFrame msec : int, H2OFrame

H2OFrame of one column containing the date in millis since the epoch.

modulo_kfold_column(n_folds=3)[source]¶

Build a fold assignments column for cross-validation. Rows are assigned a fold according to the current row number modulo n_folds.

n_folds : int

An integer specifying the number of validation sets to split the training data into.

A single column H2OFrame with the fold assignments.

month()[source]¶

Month column from a msec-since-Epoch column

mult(matrix)[source]¶

Perform matrix multiplication.

matrix : H2OFrame

The right-hand-side matrix

H2OFrame result of the matrix multiplication

na_omit()[source]¶

Remove rows with NAs from the H2OFrame.

H2OFrame

names None[source]¶

Retrieve the column names (one name per H2OVec) for this H2OFrame.

A str list of column names

nchar()[source]¶

Count the number of characters in each string of single-column H2OFrame.

A single-column H2OFrame containing the per-row character count.

ncol None[source]¶

The number of columns in the H2OFrame.

nlevels()[source]¶

Get the number of factor levels for this frame.

A dictionary of column_name:number_levels pairs.

nrow None[source]¶

The number of rows in the H2OFrame.

pop(i)[source]¶

Pop a column from the H2OFrame at index i

i : int, str

The index or name of the column to pop.

The column dropped from the frame; the frame is side-effected to lose the column

prod(na_rm=False)[source]¶

na_rm : bool, default=False

True or False to remove NAs from computation.

The product of the column.

quantile(prob=None, combine_method='interpolate')[source]¶

Compute quantiles.

prob : list, default=[0.01,0.1,0.25,0.333,0.5,0.667,0.75,0.9,0.99]

A list of probabilities of any length.

combine_method : str, default=”interpolate”

For even samples, how to combine quantiles. Should be one of [“interpolate”, “average”, “low”, “hi”]

A new H2OFrame containing the quantiles and probabilities.

rbind(data)[source]¶

Combine H2O Datasets by rows. Takes a sequence of H2O data sets and combines them by rows.

data : H2OFrame

Returns this H2OFrame with data appended row-wise.

rep_len(length_out)[source]¶

Replicates the values in data in the H2O backend

length_out : int

Number of columns of the resulting H2OFrame

H2OFrame

round(digits=0)[source]¶

Round doubles/floats to the given number of digits.

digits : int

H2OFrame

runif(seed=None)[source]¶

Generate a column of random numbers drawn from a uniform distribution [0,1) and having the same data layout as the calling H2OFrame instance.

seed : int, optional

A random seed. If None, then one will be generated.

Single-column H2OFrame filled with doubles sampled uniformly from [0,1).

scale(center=True, scale=True)[source]¶

Centers and/or scales the columns of the self._newExpr

center : bool, list

If True, then demean the data by the mean. If False, no shifting is done. If a list, then shift each column by the given amount in the list.

scale : bool, list

If True, then scale the data by the column standard deviation. If False, no scaling is done. If a list, then scale each column by the given amount in the list.

H2OFrame

sd(na_rm=False)[source]¶

Compute the standard deviation.

na_rm : bool, default=False

Remove NAs from the computation.

A list containing the standard deviation for each column (NaN for non-numeric columns).

set_level(level)[source]¶

A method to set all column values to one of the levels.

level : str

The level at which the column will be set (a string)

H2OFrame with entries set to the desired level.

set_levels(levels)[source]¶

Works on a single categorical column. New domains must be aligned with the old domains. This call has copy-on-write semantics.

levels : list

A list of strings specifying the new levels. The number of new levels must match the number of old levels.

A single-column H2OFrame with the desired levels.

set_name(col=None, name=None)[source]¶

Set the name of the column at the specified index.

col : int, str

Index of the column whose name is to be set; may be skipped for 1-column frames

name : str

The new name of the column to set

Returns self.

set_names(names)[source]¶

Change all of this H2OFrame instance’s column names.

names : list

A list of strings equal to the number of columns in the H2OFrame.

shape None[source]¶

A tuple (nrow, ncol)

show(use_pandas=False)[source]¶

Used by the H2OFrame.__repr__ method to print or display a snippet of the data frame. If called from IPython, displays an html’ized result Else prints a tabulate’d result

sign()[source]¶

signif(digits=6)[source]¶

Round doubles/floats to the given number of significant digits.

digits : int, default=6

Number of significant digits to round doubles/floats.

H2OFrame

sin()[source]¶

sinh()[source]¶

sinpi()[source]¶

split_frame(ratios=None, destination_frames=None, seed=None)[source]¶

Split a frame into distinct subsets of size determined by the given ratios. The number of subsets is always 1 more than the number of ratios given.

ratios : list

The fraction of rows for each split.

destination_frames : list

The names of the split frames.

seed : int

Used for selecting which H2OFrame a row will belong to.

A list of H2OFrame instances

sqrt()[source]¶

stratified_kfold_column(n_folds=3, seed=-1)[source]¶

Build a fold assignment column with the constraint that each fold has the same class distribution as the fold column.

n_folds: int

The number of folds to build.

seed: int

A random seed.

A single column H2OFrame with the fold assignments.

stratified_split(test_frac=0.2, seed=-1)[source]¶

Construct a column that can be used to perform a random stratified split.

test_frac : float, default=0.2

The fraction of rows that will belong to the “test”.

seed : int

For seeding the random splitting.

A categorical column of two levels “train” and “test”.

>>> my_stratified_split = my_frame["response"].stratified_split(test_frac=0.3,seed=12349453)
>>> train = my_frame[my_stratified_split=="train"]
>>> test  = my_frame[my_stratified_split=="test"]

# check the distributions among the initial frame, and the train/test frames match >>> my_frame[“response”].table()[“Count”] / my_frame[“response”].table()[“Count”].sum() >>> train[“response”].table()[“Count”] / train[“response”].table()[“Count”].sum() >>> test[“response”].table()[“Count”] / test[“response”].table()[“Count”].sum()

strsplit(pattern)[source]¶

Split the strings in the target column on the given pattern

pattern : str

The split pattern.

H2OFrame containing columns of the split strings.

structure()[source]¶

Similar to R’s str method: Compactly Display the Structure of this H2OFrame.

sub(pattern, replacement, ignore_case=False)[source]¶

Substitute the first occurrence of pattern in a string with replacement.

pattern : str

A regular expression.

replacement : str

A replacement string.

ignore_case : bool

If True then pattern will match against upper and lower case.

H2OFrame

sum(na_rm=False)[source]¶

The sum of all frame entries

summary()[source]¶

Summary: show(), plus includes min/mean/max/sigma and other rollup data

table(data2=None)[source]¶

Compute the counts of values appearing in a column, or co-occurence counts between two columns.

data2 : H2OFrame

Default is None, can be an optional single column to aggregate counts by.

H2OFrame of the counts at each combination of factor levels

tail(rows=10, cols=200)[source]¶

Analogous to Rs tail call on a data.frame.

rows : int, default=10

Number of rows starting from the bottommost

cols: int, default=200

Number of columns starting from the leftmost

An H2OFrame.

tan()[source]¶

tanh()[source]¶

tanpi()[source]¶

static temp_ctr()[source]¶

tolower()[source]¶

Translate characters from upper to lower case for a particular column

H2OFrame

toupper()[source]¶

Translate characters from lower to upper case for a particular column

H2OFrame

transpose()[source]¶

Transpose rows and columns of H2OFrame.

The transpose of the input frame.

trigamma()[source]¶

trim()[source]¶

Trim white space on the left and right of strings in a single-column H2OFrame.

H2OFrame with trimmed strings.

trunc()[source]¶

type(name)[source]¶

The type for a named column

types None[source]¶

A dictionary of column_name-type pairs.

unique()[source]¶

Extract the unique values in the column.

H2OFrame of just the unique values in the column.

var(y=None, use='everything')[source]¶

Compute the variance, or co-variance matrix.

y : H2OFrame, default=None

If y is None, then the variance is computed for self. If self has more than one column, then the covariance matrix is returned. If y is not None, then the covariance between self and y is computed (self and y must therefore both be single columns).

use : str

One of “everything”, “complete.obs”, or “all.obs”

The covariance matrix of the columns in this H2OFrame if y is given, or a eagerly computed scalar if y is not given.

week()[source]¶

Week column from a msec-since-Epoch column

which()[source]¶

Equivalent to [ index for index,value in enumerate(self) if value ]

Single-column H2OFrame filled with 0-based indices for which the elements are not zero.

year()[source]¶

Year column from a msec-since-Epoch column

GroupBy¶

class h2o.group_by.GroupBy(fr, by)[source]¶

A class that represents the group by operation on an H2OFrame.

Sample usage:

>>> my_frame = ...  # some existing H2OFrame
>>> grouped = my_frame.group_by(by=["C1","C2"])
>>> grouped.sum(col="X1",na="all").mean(col="X5",na="all").max()
>>> grouped.get_frame

Any number of aggregations may be chained together in this manner.

If no arguments are given to the aggregation (e.g. “max” in the above example), then it is assumed that the aggregation should apply to all columns but the group by columns.

The na parameter is one of [“all”,”ignore”,”rm”].

“all” - include NAs “rm” - exclude NAs

Variance (var) and standard deviation (sd) are the sample (not population) statistics.

count(na='all')[source]¶

frame None[source]¶

Returns:	the result of the group by

get_frame()[source]¶

Returns:	the result of the group by

max(col=None, na='all')[source]¶

mean(col=None, na='all')[source]¶

min(col=None, na='all')[source]¶

mode(col=None, na='all')[source]¶

sd(col=None, na='all')[source]¶

ss(col=None, na='all')[source]¶

sum(col=None, na='all')[source]¶

var(col=None, na='all')[source]¶