String to number from array

Question

Nicle Davidson 2021-9-23

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1458989-string-to-number-from-array

评论： Nicle Davidson 2021-9-23

采纳的回答： Konrad

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I have a file test.txt which I am reading the content from

the content is such as:

290729 123456

13984 654321

13272 111111

    I have it until here:
    inn = fgetl(thelist);  
    while ischar(inn)
        disp(inn)
        x = strsplit(inn);%I separate the to values in each line
        toNum=x(1,1); %want to get first value and convert it to a number
    
        theNum =double(cell2mat(toNum));%this does not work to convert {'290729'} to a number
    
        class(theNum);%trying to find out what is the type after I tried to make a number out of it
        inn = fgetl(thelist);  
    end

I need to convert this value (such as 290729 or 13984 in this case to a number)

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Answer 1

Konrad 2021-9-23

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https://ww2.mathworks.cn/matlabcentral/answers/1458989-string-to-number-from-array#answer_793364

编辑：Konrad 2021-9-23

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Hi Nicle

you need str2double() (or str2num()), not double().

double() gives you the UTF(?) code corresponding to the input string. Eg:

double('a') % = 97 or
ans = 97
double('1') % = 49
ans = 49

Conversely:

char([97 49]) % = 'a1'
ans = 'a1'

But:

str2double('1') % = 1
ans = 1

Also str2double() works on cellstrings, no need to for cell2mat():

str2double({'1' '2'}) % = 1 2
ans = 1×2
     1     2

Best, Konrad

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Konrad 2021-9-23

Then you allready converted the string to a number (note that for str2num() the input cannot be a cellstring).

Also consider Chunrus answer if your text file exclusively contains numbers as indicated in your question and if you don't need to read the file line-by-line. Then simply using load(filename,'-ascii') might also be a solution.

Nicle Davidson 2021-9-23

Yes, and thank you for both answers! It helped

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Answer 2

Chunru 2021-9-23

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https://ww2.mathworks.cn/matlabcentral/answers/1458989-string-to-number-from-array#answer_793354

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You can use "readmatrix" function:

% Generate the data file
a = [290729 123456
     13984 654321
     13272 111111];
writematrix(a, 'test.txt', 'Delimiter', ' ')
type test.txt
290729 123456
13984 654321
13272 111111
% Read the .txt file
b = readmatrix('test.txt')
b = 3×2
      290729      123456
       13984      654321
       13272      111111