How can I check if a table contains numbers only?

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Adham Elkhouly 2020-5-9

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回答： Image Analyst 2020-5-9

Good evening,

I am trying to develop a MATLAB application that adds values to a table by reading them from an excel file, but these values need to be all numbers and the x-values in the table cannot be repeated twice. Can someone please help me?

Thank you

Edit: I forgot to mention that the program works, reads the data from the sheet, writes them on the table with the readtable functiion but I cannot implement validtation.

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Mario Malic 2020-5-9

I would suggest trying to import data into a cell (or other type that will make it easier to write it to the table) variable and remove the values you don't need from there. Then write it to table.

Walter Roberson 2020-5-9

Can the x values be repeated once? 1 2 3 3 4 5 5 6 6 7 8 for example?

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Answer 1

Peng Li 2020-5-9

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I guess your question re the x-values isn't quite clear.

For the first part of your question, it is tricky to determine whether an input is a number or contains other stuffs as well. There isn't an elegent way I think. You could either try (1) to convert it to a double, if it gives you a valid double, that orignal input contains only number (or number related stuffs +-E etc), or (2) to examine whether all members of an input belong to 0123456789-+E or whatever elements you think might be used in a valid number expression (using ismember). Either way, try to import the orignal Excel sheet using '%q' option for each column to force the table to be a cell of char, and using cellfun to handle each element of the cell.

Below an example:

testTbl =
  4×2 table
       A          B   
    _______    _______
    {'123'}    {'123'}
    {'4E5'}    {'d'  }
    {'-56'}    {'67' }
    {'888'}    {'999'}
>> isNum = cellfun(@(x) all(ismember(x, '0123456789-+E')), testTbl.A);
if isNum
    testTbl.A = str2double(testTbl.A);
end
>> testTbl
testTbl =
  4×2 table
      A         B   
    _____    _______
      123    {'123'}
    4e+05    {'d'  }
      -56    {'67' }
      888    {'999'}
>> isNum = cellfun(@(x) all(ismember(x, '0123456789-+E')), testTbl.B);
if isNum
    testTbl.B = str2double(testTbl.B);
end
>> testTbl
testTbl =
  4×2 table
      A         B   
    _____    _______
      123    {'123'}
    4e+05    {'d'  }
      -56    {'67' }
      888    {'999'}