How to change a script to a function?

Question

I've got a set of data in an excel sheet that I've imported onto MATLAB however there are NaNs within that set of data. I've figured out some code in the main script to replace the NaN's into the wanted values:

max = x(:, 2);
min = x(:, 3);
for j = 1:length(max)
 for k = 1:length(min)
   if isnan (max(j))
     max (j) = ((max(j-1)+max(j+1))/2);
   elseif isnan (min(k))
     min (k) = ((min(k-1)+min(k+1))/2);
   end
 end
end

However, I need to be able to turn this code into a user-defined function and call it from the main script instead of having all the calculations on the main script.

I've tried to start making the function:

function [missingmax, missingmin] = missing(max, min)

However, I could not figure the rest out.

Adriaan · Accepted Answer · 2020-03-19 13:36:07Z

1

function [max_x, min_x] = missing(x)
max_x = x(:, 2);
min_x = x(:, 3);
for jj = 1:length(max_x)
    for kk = 1:length(min_x)
        if isnan (max_x(jj))
            max_x (jj) = ((max_x(jj-1)+max_x(jj+1))/2);
        elseif isnan (min_x(kk))
            min_x (kk) = ((min_x(kk-1)+min_x(kk+1))/2);
        end
    end
end
end

You were on the right track. Couple of things:

Your input is x, not min,max
Your outputs are min and max, not missingmax and missingmin
j denotes the imaginary unit It's not recommended for use as a variable, hence I changed it.
You called variables min and max. Don't do that. Ever. Seriously. Don't. If you manage to do min=4 and then try to calculate the minimum of an array, you'll get a bunch of errors. Basically: never use the name of a build-in function for a variable.

answered Mar 19, 2020 at 13:36

Adriaan

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2 Comments

Adriaan Over a year ago

@Kat on Stack Overflow please ask only a single question per post. For a new question, make a new post. In this case though, I'd recommend reading the MathWork's own tutorial, as this is about as basic as it goes. I presume you know how to call functions (you actually already do in your script), and had an idea why you wanted one.

Danfoa Over a year ago

Matlab functions are normally created as separate files, go to create a new function and place your function declaration there. Save the file within your working directory. Once the function is saved you can call it by its name from within any script in the working directory, without the need to "import" anything

Antoine T · Accepted Answer · 2020-03-20 20:46:47Z

0

Since you do a linear interpolation, you don't need to define a function here. It already exists in Matlab : fillmissing

So you can replace missing values in x like that

x_filled = fillmissing(x,'linear')

answered Mar 20, 2020 at 20:46

Antoine T

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