Why function need more variables

(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

Answer 1

[madhan ravi]

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()

[Zih-Sian Yang]

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]

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.