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pl-variable-output element

Displays a list of variables that are formatted for import into the supported programming languages and libraries (e.g. MATLAB, Mathematica, NumPy, R, or SymPy).

Sample element

Screenshot of the pl-variable-output element

question.html
<pl-variable-output digits="3">
  <!-- Example comment inside of this element. -->
  <pl-variable params-name="matrixC">C</pl-variable>
  <pl-variable params-name="matrixD">D</pl-variable>
</pl-variable-output>
server.py
import prairielearn as pl
import numpy as np

def generate(data):

    # Create fixed matrix
    matrixC = np.matrix("5 6; 7 8")
    matrixD = np.matrix("-1 4; 3 2")
    # Random matrices can be generated with:
    # mat = np.random.random((2, 2))

    # Export each matrix as a JSON object for the question view.
    data["params"]["matrixC"] = pl.to_json(matrixC)
    data["params"]["matrixD"] = pl.to_json(matrixD)

Customizations

Attributes for <pl-variable-output>:

Attribute Type Default Description
default-tab "matlab", "mathematica", "numpy", "r", "sympy" "matlab" Select the active tab.
digits integer 2 Number of digits to display after the decimal.
show-mathematica boolean true Toggles the display of the Mathematica tab.
show-matlab boolean true Toggles the display of the Matlab tab (also compatible with Octave).
show-numpy boolean true Toggles the display of the NumPy tab.
show-r boolean true Toggles the display of the R tab.
show-sympy boolean true Toggles the display of the SymPy tab.

Attributes for <pl-variable> (one of these for each variable to display):

Attribute Type Default Description
comment string — Comment to add after the displayed variable.
digits integer 2 Number of digits to display after the decimal for the variable. Defaults to the digits value set on the enclosing <pl-variable-output>.
params-name string — Name of variable in data["params"] to display. Required.

Migrating from deprecated attributes

The following deprecated attributes and values are still supported for backward compatibility:

Old syntax New syntax
default-tab="python" default-tab="numpy"
show-python="false" show-numpy="false"
show-python="true" show-numpy="true"

pl-matrix-output is a deprecated alias for pl-variable-output. It supports only the Matlab and NumPy tabs and always defaults to the Matlab tab. Use pl-variable-output instead.

The legacy <variable> child tag is still accepted as a deprecated alias for <pl-variable>. Use <pl-variable> instead.

Details

This element displays a list of variables inside <pl-code> tags that are formatted for import into either MATLAB, Mathematica, NumPy, R, or SymPy (the user can switch between them). Each variable must be either a scalar or a 2D numpy array (expressed as a list). Each variable will be prefixed by the text that appears between the <pl-variable> and </pl-variable> tags, followed by =. Below are samples of the format displayed under each language tab.

MATLAB format:

A = [1.23; 4.56]; % matrix

Mathematica format:

A = [1.23; 4.56]; (* matrix *)

NumPy format:

import numpy as np

A = np.array([[1.23], [4.56]]) # matrix

R format:

A = c(1.23, 4.56) # vector
A = matrix(c(1.23, 4.56, 8.90, 1.23), nrow = 2, ncol = 2, byrow = TRUE) # matrix

SymPy format:

from sympy import *

A = Matrix([[1.23], [4.56]]) # matrix

If a variable v is a complex object, you should use import prairielearn as pl and data["params"][params-name] = pl.to_json(v).

Example implementations

See also