How do I hold multiple functions in an array in MATLAB?

Question

I am new to MATLAB so I don't even know if this is possible, but here it is... I am trying to print multiple lines in a single graph using the plot function. The problem is, I want to be able to specify how many lines the graph should display by simply changing a variable, for example: {This is the pseudo code to what I want to do}

 number_of_lines = 4;
 x = 0:0.5:5;

 function_output[number_of_lines];

 for n=0:number_of_lines
     function_output[n] = sin(n + x);
 end

 for n=0:number_of_lines
     plot(x,function_output[n]);
 end

I know the above pseudo code isn't exactly MATLAB, but all I want to know if such algorithm is possible to do in MATLAB.

gnovice · Accepted Answer · 2017-08-08 05:06:35Z

2

Here's one way to implement your example in MATLAB:

function_output = zeros(numel(x), number_of_lines);  % Initialize a 2-D array
for n = 1:number_of_lines                   % MATLAB uses 1-based indexing
    function_output(:, n) = sin(n + x).';  %' Compute a row vector, transpose
                                            %   it into a column vector, and
                                            %   place the data in a column of
                                            %   the 2-D array
end
plot(x, function_output);  % This will plot one line per column of the array

And here are some documentation links you should read through to learn and understand the above code:

edited Aug 8, 2017 at 5:06

answered Dec 5, 2010 at 6:32

gnovice

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Community · Accepted Answer · 2020-06-20 09:12:55Z

1

Have you looked through the MATLAB manual? -- it is quite well-written with many examples. Copy the example scripts and paste them onto the Command Window and see what happens...

http://www.mathworks.com/help/techdoc/creating_plots/f9-53405.html

You can either write a script or use their plotting tool: http://www.mathworks.com/help/techdoc/creating_plots/f9-47085.html

--- script example

number_of_lines = 4;

x = 0:0.5:5;

function_output=ones(number_of_lines,1)*nan;

figure;hold on;

for n=1:number_of_lines

function_output(n,1) = plot(x,sin(n+x),'color',[1-n/number_of_lines 0 n/number_of_lines]);

end

legend(function_output)

Have fun .

edited Jun 20, 2020 at 9:12

CommunityBot

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answered Dec 5, 2010 at 6:46

Y.T.

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2 Comments

Y_Y Over a year ago

Question: What if I want to plot only when x is 3. Should by if statement be if( x == 3) ?

Y.T. Over a year ago

If I understood you correctly (I'm guessing here), you wish to plot only the n==3 ? In other words, you wish to plot only the 3rd line? If that is the case, yes - you can add: if (n==3); <plot the line>; end

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