what is error in this code?? {W/ textscan input)

Question

Muhammad Saad Naeem 2017-7-15

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/348865-what-is-error-in-this-code-w-textscan-input

编辑： dpb 2017-7-17

str = 'GAMMA=000 KP=123'; ;%lambda=222)
A = importdata('nmos.cir','\n');
[row , col] = size(A) ;                    
cmp = strread (str , '%s ' ) ;             
[row2 , col2] = size ( cmp ) ;
for r = 1 : 1
  first = textscan (cmp{r},'%s') ;               
  D = first{1,1};
  [var1,val1 ] = strtok(D , '=' );  
  for j = 1:row
    name = textscan(A{j} , '%s ');
    B = name{1,1};
    [row1 , col1 ] = size(B);
    for k = 1 : row1                         
      third= textscan(B{k},'%s') ;            
      C = third{1,1};
      [var2,val2] = strtok(C , '=' );         
      if (strcmp(var2 , var1))
        val2 = val1 ;     
      end
      second = strcat(var2,val2) ;
      name(k) =second ;
    end
    A{j} = name ;
  end
end

Whenever 'r' is greater than 1 it gives error

"Error using textscan
 First input must be a valid file-id or non-empty character vector.  
 Error in change_value (line 16) name = textscan(A{j} , '%s ');   "

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Muhammad Saad Naeem 2017-7-15

if r= 3: 3 or r = 2:2 no error also, error come when for loop run more than 1 time

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Answer 1

dpb 2017-7-15

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/348865-what-is-error-in-this-code-w-textscan-input#answer_274272

Note the specific text of the error message and the line it error'ed on:

"First input must be a valid file-id or non-empty character vector." (emphasis added)

"Error in change_value (line 16) name = textscan(A{j} , '%s '); "

Since A is a cellstr array from the importdata line, not a FID, and you note it does not error when r = 1, then the conclusion to be drawn is that the second element of A is empty.

Set a breakpoint at the line and inspect the content of A and all will likely be revealed.

As an aside to the actual question regarding the specific error and code, this looks like an awfully convoluted way to read a file -- why not just use textscan on the file itself?

Show us a portion of the file you're trying to read; it's probable there's a quite simpler route to the desired end than you're taking here.

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dpb 2017-7-15

"... from R2017a, ... importdata() returns string objects instead of cell array of string [T]hat can lead to code suddenly stopping working."

I'd expected when I'd asked before if the string class didn't cause some issues wrt cellstr that something like that would be the case.

dpb 2017-7-15

编辑：dpb 2017-7-17

"...find the required parameters e.g. lambda or GAMMA, replace it with user given value and then re-write the .cir file"

I'm still thinking that could be much simpler by simple string substitution within the array, couldn't it? If you're simply doing a value substitution, that ought to be fairly straightforward within a cell string (or string array altho I don't have the here to test/work with) then rewrite the modfified file from (updated) memory copy.

ADDENDUM

Specifically, using regexrep() you should be able to find the keyword of interest followed by the value and then replace the value token with the desired in a single command for each of the two elements desired.

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