How can I create and call a simple user defined function?

Question

Carlos 2013-8-20

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https://ww2.mathworks.cn/matlabcentral/answers/85182-how-can-i-create-and-call-a-simple-user-defined-function

评论： ihsan ghafoor 2023-10-13

I am trying to teach myself MATLAB with a book but I am having problems creating and calling user defined functions. Here is the code I used for area of a circle exactly as it is in the book:

     function area= calcarea(rad)
     %calcarea calculates the area of a circle
     %Format of call: calcarea(radius)
     %Returns the area
     area=pi*rad*rad; <----------Error in this line
     end

When I run it. It says Error using calcarea line 6 Not Enough Input Arguments

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ihsan ghafoor 2023-10-13

you dont have to run that file.

just write in the command window

calcarea(45)

and it will give the answer.

Never run the function file, always check it by writing the function name in command window with suitable inputs.

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Answer 1

Image Analyst 2013-8-20

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https://ww2.mathworks.cn/matlabcentral/answers/85182-how-can-i-create-and-call-a-simple-user-defined-function#answer_94674

在 MATLAB Online 中打开

You'd have to run that from a script or the command line and supply an argument for rad. Or you can put it in a function called test.m like this

function test
  % Call calcarea
  theArea = calcarea(42);
function area= calcarea(rad)
  %calcarea calculates the area of a circle
  %Format of call: calcarea(radius)
  %Returns the area
  area = pi * rad * rad;

Note, in the above you can have them both in the same m-file, but you must have the "function test()" in there because otherwise you'd have a script followed by the calcarea function and you can't mix a script and a function in the same file, but you can mix two functions in the same file.

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Stephen23 2019-7-24

编辑：Stephen23 2019-7-24

在 MATLAB Online 中打开

srinivas chappa wrote: "you should assign the value to rad."

function area=calcarea(rad)
rad=input('enter the value of radius=')
...

No, you definitely should not, because then you make the input argument rad completely useless. Using input is an awful way to provide data to a function, input arguments (exactly like the original question and answer show) are much better.

John D'Errico 2023-3-30

@Suryabhan Singh please don't add answers asking another question, even if it is semi-related to the original question.

If you are having problems, first, don't name a function with the same name as a script is is called within.

As for your subsequent problems, it is difficult to answer that, without actually seeing what you did.

I would STRONGLY suggest you spend some time reading the MATLAB Onramp tutorial.

Even after that, if you get an error, then you need to show the ENTIRE error, so everything in red. That helps us to track down what you are doing wrong. My guess is, you may not undestand the difference between a function and a script, but that is just a wild guess. So show what you wrote, and what error you got, the complete error message.

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