Show limited digits numbers.

2 次查看（过去 30 天）
armin m
armin m 2021-10-15
评论： armin m 2021-10-16
Hi i wanna numbers limited to 6 digits. For example. A=2.54357766 be show A=2.543578. Tnx
  2 个评论
Cris LaPierre
Cris LaPierre 2021-10-16
Where do you want this to be shown?
armin m
armin m 2021-10-16
编辑：armin m 2021-10-16
Command windows and every where i wanna to print. E.g .txt file from diary on mode. But my main purpose relate to calculation. I have ref. Which calculated accordding to 6 digits numbers so i think the numbers with for example 10 digits have effect on result. So i wanna decrease digits to 6 to compare my results with reference.

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回答（1 个）

Chunru
Chunru 2021-10-16
Ran in:
You can use fprintf with format specifier to format the print out. "doc fprintf".
A=2.54357766;
fprintf('%.6f\n', A);
2.543578
  2 个评论
Walter Roberson
Walter Roberson 2021-10-16
Ran in:
Note that doing so will not change the result. If you are concerned that "10 digits have effect on results" and you want to decrease the digits to 6 for calculation purpose, then you are not going to achieve your aims just by using fprintf()
Perhaps what you are looking for is
format long g
A=2.54357766
A =
2.54357766
B = round(A, 6)
B =
2.543578
If so, then be careful: MATLAB does not use decimal calculations, and 0.1 is not exactly reprepresentable in binary calculations, so round(,6) is not actually rounding to 6 decimal places, only to as close as it can get:
fprintf('%.999g\n', B)
2.543578000000000116642695502378046512603759765625
That is the exact binary representation that is used.
If you need calculations done in 6 decimal places, then you have three choices:
  1. Use the Symbolic Toolbox... and worry about the effect of the 5 hidden guard digits during calculations; or
  2. Calculate in integer ratios, perhaps using John D'Errico's Variable Precision Integer package; or
  3. Use the Fixed Point Toolbox

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