Created by Nishant Kheterpal and Jessica Hu
In the examples in the left column, np
refers to the NumPy module, as usual. Everything else is a function, a method, an example of an argument to a function or method, or an example of an object we might call the method on. For example, tbl
refers to a table, array
refers to an array, and num
refers to a number. array.item(0)
is an example call for the method item
, and in that example, array
is the name previously given to some array.
Name  Chapter  Description  Input  Output 

Table() 
6  Create an empty table, usually to extend with data  None  An empty Table 
Table().read_table(filename) 
6  Create a table from a data file  string: the name of the file  Table with the contents of the data file 
tbl.with_columns(name, values) tbl.with_columns(n1, v1, n2, v2,...) 
6  A table with an additional or replaced column or columns. name is a string for the name of a column, values is an array 
1. string: the name of the new column; 2. array: the values in that column 
Table: a copy of the original Table with the new columns added 
tbl.column(column_name_or_index) 
6  The values of a column (an array)  string or int: the column name or index  array: the values in that column 
tbl.num_rows 
6  Compute the number of rows in a table  None  int: the number of rows in the table 
tbl.num_columns 
6  Compute the number of columns in a table  None  int: the number of columns in the table 
tbl.labels 
6  Lists the column labels in a table  None  array: the names of each column (as strings) in the table 
tbl.select(col1, col2, ...) 
6  Create a copy of a table with only some of the columns. Each column is the column name or index.  string or int: column name(s) or index(es)  Table with the selected columns 
tbl.drop(col1, col2, ...) 
6  Create a copy of a table without some of the columns. Each column is the column name or index.  string or int: column name(s) or index(es)  Table without the selected columns 
tbl.relabeled(old_label, new_label) 
6  Returns a new table with the column heading in the first argument changed to the second  1. string: the old column name 2. string: the new column name 
None: modifies the original Table 
tbl.relabel(old_label, new_label) 
6  Modifies the existing table in place, changing the column heading in the first argument to the second  1. string: the old column name 2. string: the new column name 
Table: a copy of the original with the changed label 
tbl.sort(column_name_or_index) 
6.1  Create a copy of a table sorted by the values in a column. Defaults to ascending order unless descending = True is included. 
1. string or int: column index or name 2. (Optional) descending = True 

tbl.where(column, predicate) 
6.2  Create a copy of a table with only the rows that match some predicate See Table.where predicates below. 
1. string or int: column name or index 2. are.(...) predicate 

tbl.take(row_indices) 
6.2  A table with only the rows at the given indices. row_indices is an array of indices. 
array of ints: the indices of the rows to be included in the Table  Table: a copy of the original with only the rows at the given indices 
tbl.scatter(x_column, y_column) 
7  Draws a scatter plot consisting of one point for each row of the table. Note that x_column and y_column must be strings specifying column names. 
1. string: name of the column on the xaxis 2. string: name of the column on the yaxis 
None: draws a scatter plot 
tbl.plot(x_column, y_column) 
7  Draw a line graph consisting of one point for each row of the table.  1. string: name of the column on the xaxis 2. string: name of the column on the yaxis 
None: draws a line graph 
tbl.barh(categories) tbl.barh(categories, values) 
7.1  Displays a bar chart with bars for each category in a column, with height proportional to the corresponding frequency. values argument unnecessary if table has only a column of categories and a column of values.  1. string: name of the column with categories 2. (Optional) string: the name of the column with values for corresponding categories 
None: draws a bar chart 
tbl.hist(column, unit, bins) 
7.2  Generates a histogram of the numerical values in a column. unit and bins are optional arguments, used to label the axes and group the values into intervals (bins), respectively. Bins have the form [a, b) , where a is included in the bin and b is not. 
1. string: name of the column with categories 2. (Optional) string: units of xaxis 3. (Optional) array of ints/floats denoting bin boundaries 
None: draws a histogram 
tbl.apply(function, column) 
8.1  Returns an array of values resulting from applying a function to each item in a column.  1. function: function to apply to column 2. string: name of the column to apply function to 
array: contains an element for each value in the original column after applying the function to it 
tbl.group(column_or_columns, func) 
8.2  Group rows by unique values or combinations of values in a column(s). Multiple columns must be entered in array or list form. Other values aggregated by count (default) or optional argument func . 
1. string or array of strings: column(s) on which to group 2. (Optional) function: function to aggregate values in cells (defaults to count) 
Table: a new Table 
tbl.pivot(col1, col2, vals, collect) tbl.pivot(col1, col2) 
8.3  A pivot table where each unique value in col1 has its own column and each unique value in ccol2 has its own row. Count or aggregate values from a third column, collect with some function. Default vals and collect return counts in cells. 
1. string: name of column whose unique values will make up columns of pivot table 2. string: name of column whose unique values will make up rows of pivot table 3. (Optional) string: name of column that describes the values of cell 4. (Optional) function: how the values are collected, e.g. sum or np.mean 
Table: a new Table 
tblA.join(colA, tblB, colB) tblA.join(colA, tblB) 
8.4  Generate a table with the columns of tblA and tblB, containing rows for all values of a column that appear in both tables. Default colB is colA . colA and colB must be strings specifying column names. 
1. string: name of column in tblA with values to join on 2. Table: other Table 3. (Optional) string: if column names are different between Tables, the name of the shared column in tblB 
Table: a new Table 
tbl.sample(n) tbl.sample(n, with_replacement) 
10  A new table where n rows are randomly sampled from the original table. Default is with replacement. For sampling without replacement, use argument with_replacement=False . For a nonuniform sample, provide a third argument weights=distribution where distribution is an array or list containing the probability of each row. 
1. int: sample size 2. (Optional) with_replacement=True 
Table: a new Table with n rows 
Name  Chapter  Description 

max(array) 
3.3  Returns the maximum value of an array 
min(array) 
3.3  Returns the minimum value of an array 
sum(array) 
3.3  Returns the sum of the values in an array 
abs(num), np.abs(array) 
3.3  Take the absolute value of number or each number in an array. 
round(num), np.round(array) 
3.3  Round number or array of numbers to the nearest integer. 
len(array) 
3.3  Returns the length (number of elements) of an array 
make_array(val1, val2, ...) 
5  Makes a numpy array with the values passed in 
np.average(array) np.mean(array) 
5.1  Returns the mean value of an array 
np.diff(array) 
5.1  Returns a new array of size len(arr)1 with elements equal to the difference between adjacent elements; val_2  val_1, val_3  val_2, etc. 
np.sqrt(array) 
5.1  Returns an array with the square root of each element 
np.arange(start, stop, step) np.arange(start, stop) np.arange(stop) 
5.2  An array of numbers starting with start , going up in increments of step , and going up to but excluding stop . When start and/or step are left out, default values are used in their place. Default step is 1; default start is 0. 
array.item(index) 
5.3  Returns the ith item in an array (remember Python indices start at 0!) 
np.random.choice(array, n) np.random.choice(array) 
9  Picks one (by default) or some number 'n' of items from an array at random. By default, with replacement. 
np.count_nonzero(array) 
9  Returns the number of nonzero (or True ) elements in an array. 
np.append(array, item) 
9.2  Returns a copy of the input array with item (must be the same type as the other entries in the array) appended to the end. 
percentile(percentile, array) 
12.1  Returns the corresponding percentile of an array. 
Table.where
PredicatesAny of these predicates can be negated by adding not_
in front of them, e.g. are.not_equal_to(Z)
or are.not_containing(S)
.
Predicate  Description 

are.equal_to(Z) 
Equal to Z 
are.above(x) 
Greater than x 
are.above_or_equal_to(x) 
Greater than or equal to x 
are.below(x) 
Less than x 
are.below_or_equal_to(x) 
Less than or equal to x 
are.between(x,y) 
Greater than or equal to x and less than y 
are.between_or_equal_to(x,y) 
Greater than or equal to x , and less than or equal to y 
are.contained_in(A) 
Is a substring of A (if A is a string) or an element of A (if A is a list/array) 
are.containing(S) 
Contains the string S 
are.strictly_between(x,y) 
Greater than x and less than y 
These are functions in the datascience
library that are used in the course that don't fall into any of the categories above.
Name  Chapter  Description  Input  Output 

sample_proportions(sample_size, model_proportions) 
11.1  Sample_size should be an integer, model_proportions an array of probabilities that sum up to 1. The function samples sample_size objects from the distribution specified by model_proportions . It returns an array with the same size as model_proportions . Each item in the array corresponds to the proportion of times it was sampled out of the sample_size times. 
1. int: sample size 2. array: an array of proportions that should sum to 1 
array: each item corresponds to the proportion of times that corresponding item was sampled from model_proportions in sample_size draws, should sum to 1 
minimize(function) 
15.4  Returns an array of values such that if each value in the array was passed into function as arguments, it would minimize the output value of function . 
function: name of a function that will be minimized.  array: An array in which each element corresponds to an argument that minimizes the output of the function. Values in the array are listed based on the order they are passed into the function; the first element in the array is also going to be the first value passed into the function. 