Round the elements column of the matrix to the same digit than it is in the other column

Question

Laszlo Sleisz 2021-7-14

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https://ww2.mathworks.cn/matlabcentral/answers/878178-round-the-elements-column-of-the-matrix-to-the-same-digit-than-it-is-in-the-other-column

回答： Stephen23 2021-7-15

采纳的回答： Matt J

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I round elements one of column of matrix to 2 significant digits:

Result(:,5) = round(Result(:,5),2,'significant');

I wold like to round the elements another column of the same matrix to exactly same digits than it is in 'significant' digit column.

Is there any way to read back the number of digits from the 'significant' digit column to use it in other column?

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Answer 1

Matt J 2021-7-14

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编辑：Matt J 2021-7-14

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One way,

Result(:,5) = round(Result(:,5),2,'significant');
numDigits=strlength(extractAfter(string(Result(:,5)),'.'));
numDigits(isnan(numDigits))=0

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Matt J 2021-7-14

Thank you, now it works.

You are welcome, but please Accept-click the answer to indicate so.

Is it possible to format the number to N digits to the right of the decimal point, delete the unnecessary zeros.

Only if the array is converted to a string. If you plan to work with Result as numeric data, the only control you have over how it is displayed is through the format() command.

Laszlo Sleisz 2021-7-15

I think in this case I should use Cell array, because as I know not possible to create one matrix with different data type.

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Answer 2

Stephen23 2021-7-15

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https://ww2.mathworks.cn/matlabcentral/answers/878178-round-the-elements-column-of-the-matrix-to-the-same-digit-than-it-is-in-the-other-column#answer_747173

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S = 2;
A = 32*rand(5,7)-13
A = 5×7
   -8.9001  -12.7270    9.5712   14.7717    6.2782    3.5775   10.7267
   16.4892    2.1012   12.5711    0.2720    8.0913  -11.5669   -9.3372
   -5.9647  -12.7967    3.1765    5.9842   12.7080   15.4362   -4.9144
   -8.0932  -12.6045    6.2981   14.2722   -9.1178    8.2538   -3.3988
   15.7385    0.4380    2.9713   -6.0512    2.5839   -9.1609   -4.6357
round(A(:,5),S,'significant') % for comparison
ans = 5×1
    6.3000
    8.1000
   13.0000
   -9.1000
    2.6000
P = S-1-floor(log10(abs(A(:,5))));
B = round(A.*10.^P)./(10.^P)
B = 5×7
   -8.9000  -12.7000    9.6000   14.8000    6.3000    3.6000   10.7000
   16.5000    2.1000   12.6000    0.3000    8.1000  -11.6000   -9.3000
   -6.0000  -13.0000    3.0000    6.0000   13.0000   15.0000   -5.0000
   -8.1000  -12.6000    6.3000   14.3000   -9.1000    8.3000   -3.4000
   15.7000    0.4000    3.0000   -6.1000    2.6000   -9.2000   -4.6000