error using function code

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Matt Thomas
Matt Thomas on 16 May 2022
Commented: Cris LaPierre on 17 May 2022
I have an assignment due soon and i can not get matlab to work. I have never used matlab before and this is my first asignment in it. I have to make a program where i input a score fom 0 to 100 and it tells me what the grade is.
the first line of code needs to be
function grade = lettergrade(score)
but every time i try this, i get a error and matlab will not let me proced. I have even tried to copy someones code and it fails. I even copied the example from my book by copy paste and it throws the same error
error: function definition not supported in this context. functions can only be created as local or nested functions
no idea what the heck this even means

Answers (2)

James Tursa
James Tursa on 16 May 2022
Edited: James Tursa on 17 May 2022
Create a file called lettergrade.m somewhere on the MATLAB path (e.g., in your working directory)
edit lettergrade.m
Copy all of your lettergrade function code into that file and save it.
Then simply call the lettergrade function like you would call any other function. From the command line or from within another file.
The reason what you are currently doing isn't working is because MATLAB thinks you are trying to create a function on the fly at the command line.
Note that if you were trying to create a function called "grade" as your example code shows, you would create a file called grade.m rather than lettergrade.m (but your instructions are to create a function called lettergrade)
James Tursa
James Tursa on 17 May 2022
It does both. If the file already exists then it will edit the file. If the file doesn't exist then it will create it.

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Voss on 17 May 2022
This error means you cannot define a function on the MATLAB command-line. You need to create an m-file and define the function in there.
For example, if your function should be called lettergrade, you can enter
edit lettergrade
on the command-line (and say yes if MATLAB asks you if you want to create a new m-file).
Then put the code in there, with the first line being:
function grade = lettergrade(score)
After that's done, then you can run the function from the command-line or from other functions (or from scripts, which are also m-files) by doing, say,
my_grade = lettergrade(84);
which should store the value 'B' in the variable my_grade, since an 84 should be a B.
Cris LaPierre
Cris LaPierre on 17 May 2022
See this page on creating functions in file:
Ch 12 of MATLAB Onramp coversthe basics of if statements and for loops.

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