How to make this code as a function?

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R7 DR 2015-3-25

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关闭： MATLAB Answer Bot 2021-8-20

Hi

I want to make the following code as a function. I want to call this code as function in another code to get the 'T' values.

[T_20]=xlsread('20.xlsx','sheet2','C2:C2243')
[alpha_20]=xlsread('20.xlsx','sheet2','F2:F12243')
for i=1:8
    x(1)=0.1
    x(2)=0.2
    x(i+1)=x(i)+0.1
    for j=2:2242
        if     x(i)>alpha_20(j) 
            X2_20(i)=alpha_20(j+1)
            X1_20(i)=alpha_20(j)
            Y2_20(i)=T_20(j+1)
            Y1_20(i)=T_20(j)
          end
      end
      T (i)=(((Y2_20(i)-Y1_20(i))/(X2_20(i)-X1_20(i)))*(x(i)-X1_20(i)))+Y1_20(i)
    end
Thanks

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Answer 1

Star Strider 2015-3-25

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See the documentation for Function Basics to get you started.

You already know you want it to return ‘T’, so you need to define what (if any) inputs you want for your function

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Star Strider 2015-3-26

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My pleasure.

I’m not certain that I understand exactly what you want to do. If the Excel sheets are all the same format so the column references don’t change, but only the file name changes, then if I understand correctly, you simply need to pass the file prefix (as a string) to your function and have it return ‘T’.

For instance, your function (I named it ‘ExcelRead’ here) would have its first three lines as:

function T = ExcelRead(prefix)
[T_20]=xlsread([prefix '.xlsx'],'sheet2','C2:C2243')
[alpha_20]=xlsread([prefix '.xlsx'],'sheet2','F2:F12243')
          ... REST OF CODE ...
end

and you would then call it as:

prefix = '20';
T = ExcelRead(prefix);

If you’re going to call it several times in a single function and need to store all the ‘T’ values, consider saving ‘T’ as a multi-dimensional array or a cell array, adding a new ‘page’ or cell element for each call.

For example:

for k1 = 1:something
    prefix = filenumberstring(k1,:);
    T(:,:,k1) = ExcelRead(prefix);
         ... OTHER CODE ...
end

or for a cell array, the ‘ExcelRead’ call would be:

T{k1} = ExcelRead(prefix);

Note the curly brackets ‘{}’ indicating a cell element.

Is this the sort of thing you want to do?

Star Strider 2015-3-26

在 MATLAB Online 中打开

The ‘filenumberstring’ variable is intended to represent whatever the prefix of your file is, depending on how you store it. It is yours to define. In your illustration, it might be:

filenumerstring = '20';

it could also be:

filenumber = [20, 25, 31, 42];
for k1 = 1:length(filenumber)
    prefix = num2str(filenumber(k1), '%02d');
    T{k1} = ExcelRead(prefix);
    ... ETC ...
end

or whatever you want.

the ‘something’ reference is the length of the array in which you have stored your file numbers.

Dynamically naming variables such as ‘T20’ for filename '20.xlsx' is not good programming practice. The ‘k1’ reference for each value of ‘T’ will keep them easily accessible. Each ‘T{k1}’ (using cell notation) corresponds to ‘filenumber(k1)’, where filenumber are the number names you hve given your files. It is then easy to cross-reference them by ‘filenumber’.

There are many different ways to structure your code, some better than others, and each way taken in the context of what you are doing. I haven’t seen how you’ve structured the rest of your code, so I’m guessing as to how to structure the loop.

R7 DR 2015-3-27

Thanks. Its working. I did a mistake by calling the 'T' and 'D' separately in the main code.

I came up with one more doubt. I need to plot the graph between the 'T_a' (loaded from excel) and 'D'(calculated in the loop) for each file in a single figure. As we are not storing the data loaded from excel files, how to make the graph?

we must store the 'T_a' values to plot the graph (or) we have some other alternative approach?

Thanks