Automating inputs to Matlab

Question

I'm helping out with grading in a Matlab course this summer and one of the assignments consists of building a simple user interface for plotting functions and altering their appearance. All the input is done to the command-line, so the menus look something like:

=====================
1. New function
2. Change line-width
3. Change line-style
=====================

I always start out testing the same way when grading to test basic functionality:

1, 2, sin(x) (create a graph of sin(x) in window 2)

1, 3, exp(x) (create a graph of exp(x) in window 3)

2, 3, 2 (change the line-width of plot number 3 to 2)

3, 2, -- (change the line-style of plot number 2 to dashed)

etc.

Since the majority of hand-ins follow the same suggested menu structure it would make my life easier if there was a way to automatically do these inputs with a script instead of repeating the same sequence of numbers and letters over and over. The script itself doesn't have to be in Matlab although I'm guessing it would be practical since I need to check the resulting graphs manually (i.e. I need the input to be entered into the Matlab-command line).

Basically I want Matlab to read the keystrokes "1 [enter] 2 [enter] sin(x) [enter] ..." to the command-line while running another Matlab-script.

Any ideas?

Amro Amro · Accepted Answer · 2011-08-11T20:43:32

One possibility is to create a private version of the input function that shadows the built-in one. Each time it is called, it returns a value from a predetermined set of values. You can maintain the state using a global/persistent variable (a counter to keep track of how many times the function was called).

Basically you would be creating a method stub to mock the behavior of the real function.

Here is an example to better explain my idea:

/somepath/private/input.m

function ret = input(prompt, varargin)
    %# counter
    persistent count
    if isempty(count), count = 1; end

    %# hard-coded values to return
    values = {
        1 2 'sin(x)' ...
        1 3 'exp(x)' ...
        2 3 2 ...
        3 2 '--' ...
    };

    %# display the prompt message
    disp([prompt '[SIMULATED INPUT #' num2str(count) ']'])

    %# return value
    ret = values{count};

    %# increment counter
    count = count + 1;
    if count>12
        count = 1;
    end
end

/somepath/hw1.m

function hw1
    %# image this is a sample homework file, 
    %# using the standard INPUT function to ask for input from the user
    %# and do something useful with it :)

    num1 = input('enter a number: ');
    num2 = input('enter a second number: ');
    str = input('enter a string: ', 's');
    fprintf('You entered: %d %d %s\n',num1,num2,str);

    num1 = input('enter a number: ');
    num2 = input('enter a second number: ');
    str = input('enter a string: ', 's');
    fprintf('You entered: %d %d %s\n',num1,num2,str);

    num1 = input('enter a number: ');
    num2 = input('enter a second number: ');
    num3 = input('enter a third number: ');
    fprintf('You entered: %d %d %d\n',num1,num2,num3);

    num1 = input('enter a number: ');
    num2 = input('enter a second number: ');
    str = input('enter a string: ', 's');
    fprintf('You entered: %d %d %s\n',num1,num2,str);
end

This is the output you get:

enter a number: [SIMULATED INPUT #1]
enter a second number: [SIMULATED INPUT #2]
enter a string: [SIMULATED INPUT #3]
You entered: 1 2 sin(x)
enter a number: [SIMULATED INPUT #4]
enter a second number: [SIMULATED INPUT #5]
enter a string: [SIMULATED INPUT #6]
You entered: 1 3 exp(x)
enter a number: [SIMULATED INPUT #7]
enter a second number: [SIMULATED INPUT #8]
enter a third number: [SIMULATED INPUT #9]
You entered: 2 3 2
enter a number: [SIMULATED INPUT #10]
enter a second number: [SIMULATED INPUT #11]
enter a string: [SIMULATED INPUT #12]
You entered: 3 2 --

Automating inputs to Matlab

2 Answers

/somepath/private/input.m

/somepath/hw1.m