Not enough input arguments

Question

Daniel Wang 2022-1-20

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1632885-not-enough-input-arguments

评论： Image Analyst 2022-1-20

function [out]=loadrpc(filename, mnchs, flag)
%   mnchs: array, the selected channels to be read.
%         if empty, read all data
%   flag: the same as Matlab fopen's MACHINEFORMAT
%         'l': ieee-little-endian, such as NT
%         'b': ieee-big-endian, such as UNIX
%          default is 'l'
%
%   example:
%		y=loadrpc('test.rsp');  %read all data 
%       z=loadrpc('test.rsp', [2, 10 20]);  %read channel: 2, 10, and 20
%
if (nargin==1)
   mnchs='';
   flag='l';
   mnchs_n=0;   
elseif ((nargin==2) & ~isempty(mnchs))
   flag='l';
   mnchs_n=max(size(mnchs));
elseif ((nargin==3) & ~isempty(mnchs))
   mnchs_n=max(size(mnchs));
else
   mnchs='';
   mnchs_n=0;   
end
fid=fopen(filename, 'r', flag);
if (fid == -1) 
   out=0;
   return;
end

Repurposing some old code written 20 years ago. This code represents the first part of a function used to read the values of .rsp files (binary format; time history data). 'Not enough input arguments' error ocurs at the line: fid=fopen(filename, 'r', flag);

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Torsten 2022-1-20

You can not simply run this function "loadrpc".

You must call it with appropriate input arguments for filename, mnchs and flag.

Daniel Wang 2022-1-20

I thought that the code I shared defines the function. I would call the function name AFTER the function is defined with the appropriate inputs, right? In which case, the error still comes up during the definition stage.

To get past this error I had to define the input arguments before the function. Is this common practice? I'm very new to functions in MATLAB

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Answer 1

Image Analyst 2022-1-20

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1632885-not-enough-input-arguments#answer_878580

Wow - bad, fragile code. Not robust at all. For example it does not check filename to see if it's empty. And does check with isfile(filename) to see if it exists before trying to open it.

Anyway, what did you pass in for filename, mnchs, and flag when you called the function?

You didn't just press the green run triangle without assigning values to those variables did you? Because it obviously needs a filename to call fopen(). It can't be just null.

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Daniel Wang 2022-1-20

I thought that the code I shared defines the function. I would call the function name AFTER the function is defined with the appropriate inputs, right? In which case, the error still comes up during the definition stage.

To get past this error I had to define the input arguments before the function. Is this common practice? I'm very new to functions in MATLAB

Image Analyst 2022-1-20

在 MATLAB Online 中打开

Yes, of course. That defines the function but not the variables. So, in your main program when you get to this line:

[out]=loadrpc(filename, mnchs, flag)

if you haven't defined filename, mnchs, flag, what is it supposed to use for those values? Just make up something? What if you wanted 'test.dat', 5, and 'b' and you didn't pass those in? Is it okay if the program makes up and uses "bogus.dat", 9, and 'l" instead? That might not do what you want. So you have to tell it what you want.

So, like

[out]=loadrpc('mydata.dat', 4, 'b');

or whatever you want/need.

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