fprintf Displays the wrong value

Question

J 2014-10-22

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/159596-fprintf-displays-the-wrong-value

编辑： J 2014-10-22

采纳的回答： Image Analyst

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The following command returns the wrong value when using the command:

fprintf('\ny = %1.2f\n\n',y);

Enter a value for x: 5

y = 45.00

y = 52.00

Here is the code:

    clear all; clc
    x = input('Enter a value for x: ');
    if x == -2 || x == -6 || x == -4;
        y = '3';
    elseif x == 2;
        y = '0';
    else
        error('Error');
    end
    clc
    % display(y);
    fprintf('\ny = %1.2f\n\n',y);

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Answer 1

Image Analyst 2014-10-22

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https://ww2.mathworks.cn/matlabcentral/answers/159596-fprintf-displays-the-wrong-value#answer_156120

编辑：Image Analyst 2014-10-22

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You're setting y equal to a character string but using %1.2f (which doesn't make sense even if y were a double) instead of %s to display a character string. So it displays the ASCII values of the string. Instead of

y = '0'; % y is a character.

and so on, try

y = 0; % y is a double.

and use %d to display it, not %1.2f, in your fprintf() call.

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J 2014-10-22

I can't believe I missed that. Thank you.

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Answer 2

Roger Stafford 2014-10-22

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https://ww2.mathworks.cn/matlabcentral/answers/159596-fprintf-displays-the-wrong-value#answer_156119

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You are assigning y string values, not numerical values, but you are displaying them using 'fprintf' for numerical values (%1.2f), so you have to expect strange results. For example the string value of y = '3' has a corresponding numerical value of 51.

Also you have written

if x == -2 x == -6 x == -4;

but that will not behave as I think you expect. Better read up on the 'if' function to see how to write a valid 'if' condition.