Why function need more variables

Question

Zih-Sian Yang 2019-8-8

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/475452-why-function-need-more-variables

编辑： madhan ravi 2019-8-8

(I'm a beginner of matlab. )

I try to make a matlab sub-function to analysis the frequency of our lab data,however,matlab always display "Not enough input arguments."

I can't fix error of my program.

What should I add or change?

function f = freq(time,data)
    t = time;
    d = data;
    max = islocalmax(data);
    dmax = d(max);
    tmax = t(max); %the t of vmax
    for i = 1 : length(dmax)-2
        period(i) = tmax(i+2) - tmax(i);
    end
    f = 1/mean(period);
end

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Answer 1

madhan ravi 2019-8-8

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/475452-why-function-need-more-variables#answer_386830

编辑：madhan ravi 2019-8-8

在 MATLAB Online 中打开

time = ... some values
data = ... some values
f = freq(time,data) % this is how you call a function

Google "how to call a function MATLAB?"

Note: Don't use max as variable name because MATLAB has an inbuilt function named max()

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Zih-Sian Yang 2019-8-8

编辑：Zih-Sian Yang 2019-8-8

在 MATLAB Online 中打开

I have used for loop to analysis the same data before,now,I want to creat a sub-function ,by chaning my for loop,to use. I want to know why program need more input argument.

In C,

double freq(double time,double data)
{
    .
    .
    .
    
    We can declare variable in there.
    .
    .
    .
    
}
    

Why can't MATLAB declare variables in sub-functions?

I try to fixed by using global variables .

function f = freq(time,data)
    global t d max dmax tmax
    max = islocalmax(data);
    dmax = d(max);
    tmax = t(max); %the t of vmax
    for i = 1 : length(dmax)-2
        period(i) = tmax(i+2) - tmax(i);
    end
    f = 1/mean(period);
end

However,it still display "Not enough input arguments." in command window.

madhan ravi 2019-8-8

编辑：madhan ravi 2019-8-8

https://in.mathworks.com/help/matlab/math/parameterizing-functions.html - the link shows you how to parameterize a function , plus you need to call the function properly with passing in the adequate amount of arguments to the function as shown in the answer above. Don‘t use global!, it’s completely avoidable.

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