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    • Thread Starter

    It's a question on MatLab Integration program, but have a look at this code first. It's a part of the Integration on Rectangle Method program:

    [LINES 1-3]
    x = 1 : 2 : 5; % x=lower limit: strip width: upper limit
    % These are not supposed to be constants, but for this question's simplicity, let's keep it that way.

    [LINE 4]
    y_x = input ( 'Enter your function of x = ' )
    % allowing the user to modify the function as required

    [LINE 5]
    S = 2 .* ( sum (abs (y_x)) )

    Now, that works fine with the subsequent lines to calculate the approximation of the integration; but, I want what was input by the user for y_x to be also used for the plot TITLE, DISP, and others. The issue is y_x turns to an array instantly. If I turn the input into string [Ex: y_x = input ( ' Enter you function of x = ' , 's') ], it works with the DISP and TITLE, but it doesn't process the x array, so I don't get the integration approximation. Example, say x.^2 was input. Hence, y_x = x.^2

    [LINE 6 - 7]
    plot( x , y_x)
    title(['Numeric Integration for' , num2str(y_x) , 'with 2 slices')

    Instead of title being 'Numeric Integration for x.^2 with 2 slices', what shows is 'Numeric Integration for 1 9 25 with 2 slices.' [1 9 25] is the squares for x=1 : 2 : 5. That's because the input has turned to an array and info is lost. Anyone knows how to get around this problem?

    mmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm chemeng
    • Thread Starter

    LOL no wonder I thought the reply was pretty quick

    I did a bit of googling and found this: http://www.mathworks.co.uk/help/matlab/ref/eval.html

    x = 1 : 2 : 5;
    y_x = input ('Enter your function of x = ','s');
    y_eval = eval(y_x);
    S = 2 .* sum(abs(y_eval))
    plot( x , y_eval)
    title(['Numeric Integration for ',num2str(y_x),' with 2 slices'])
    You can do something like the above. Its a simple change once you use the eval() function.
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