readtable and strcmp returning 0 all the time

Question

Mini Me 2016-11-17

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评论： Peter Perkins 2016-11-18

I am comparing a string that is in my excel csv file that I read in matlab using readtable because it has numbers and strings with special characters in it.

I set my string: Str = 'var'

keep in mind in readtable in the excel sheet there's no ' ' around the string but readtable inserts it.

now I am trying to compare my string to what's in readtable an it keeps returning 0 when it should be 1.

The data in the table always display the header, may that be the reason why it never matches the string? How can I fix it?

fid = readtable('filename')
C = zeros(1,size(fid,1));
Str = 'var';
for k = 1: 10
      tf=strcmp(fid(k,28), Str ) ;
      if tf == 1
          C(k) = Yes;
      else
          C(k) = No;
      end
end

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Answer 1

Walter Roberson 2016-11-17

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The basic problem that you are having is that fid(k,28) is a table not the contents stored at that location. You need fid{k,28} to get the contents.

A shorter version of your code would be to remove the for loop and

vals = [No, Yes];
C(1:10) = vals( 1 + strcmp(fid{1:10,28}, Str) );

If No is 0 and Yes is 1 then

C(1:10) = strcmp(fid{1:10,28}, Str);

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Walter Roberson 2016-11-17

Those are two different ways. The second single-line version is appropriate only in the case where No == 0 and Yes == 1.

Peter Perkins 2016-11-18

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Without meaning to muddy the waters, if you're only accessing one variable in the table at a time, you might find that

fid.Var28(1:10)

is more readable than

fid{1:10,28}

Some people prefer the dot to the braces. In any case, one of the benefits of tables is that you can use a meeaningful name, rather than a number like 28. So even

fid{k,'Var28'}

might be preferable. Of course, "Var28' probably isn't the name that readtable will create from the file, you would use whatever that is.

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