Help displaying a formatted matrix to the command window

2012 6 5
3 个回答
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更新时间：2018 10 10
37 次查看（30 天）

1 个投票

Hi all, this seems like a simple question, but sprintf(...) doesn't do the trick. Is there an EASY way to display a matrix in the command window with a specified number of digits of precision?
EXAMPLE:
>> x = rand(3,2) - 0.5
x =
-0.3810 -0.1596
-0.0016 0.0853
0.4597 -0.2762
>> format long >> x
x =
-0.381002318441623 -0.159614273333867
-0.001635948017857 0.085267750979777
0.459743958516081 -0.276188060508863
How do I show x with, say, 6 digits of precision (as in below)??
-0.381002 -0.159614
-0.001635 0.085267
0.459743 -0.276188
I'm sure one could write a code that figured out the size of x and then used sprintf to create the desired output. Does this code exist?

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更多回答（2 个）

Oleg Komarov
Oleg Komarov 2012-6-5

3 个投票

Please read more carefully the documentation of sprintf(), it DOES the trick:
sprintf('%.6f %.6f\n',rand(3,2))
Edited
Now, if you wanna make the number of columns adjust automatically, then:
A = randn(3,9);
sprintf([repmat('%10.6f',1,size(A,2)) '\n'],A)
Unfortunately, there's some learning curve in format customization.

7 个评论
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Brenden Epps
Brenden Epps 2012-6-5
Hi Oleg, thanks for your quick reply. Yes, the whole point was to automate sprintf... What can be done about the issue of negative signs? sprintf fails in that case:
A = rand(3,9);
sprintf([repmat('%.6f',1,size(A,2) '\n'],A)
??? sprintf([repmat('%.6f',1,size(A,2) '\n'],A)
|
Error: Unexpected MATLAB expression.
>> sprintf([repmat('%.6f ',1,size(A,2)),'\n'],A)
ans =
0.751267 0.255095 0.505957 0.699077 0.890903 0.959291 0.547216 0.138624 0.149294
0.257508 0.840717 0.254282 0.814285 0.243525 0.929264 0.349984 0.196595 0.251084
0.616045 0.473289 0.351660 0.830829 0.585264 0.549724 0.917194 0.285839 0.757200
>> A = rand(3,9)-0.5;
>> sprintf([repmat('%.6f ',1,size(A,2)),'\n'],A)
ans =
0.253729 -0.119554 0.067822 -0.424146 -0.446050 0.030798 0.279167 0.434011 -0.370094
0.068824 -0.030609 -0.488098 -0.162877 -0.337818 0.294285 -0.188785 0.028533 -0.334351
0.101982 -0.237029 0.154079 0.189215 0.248152 -0.049458 -0.416179 -0.271023 0.413337
Oleg Komarov
Oleg Komarov 2012-6-5
I edited the second solution, now it's correct.
Brenden Epps
Brenden Epps 2012-6-6
Thanks Oleg. I was hoping that the numbers would be aligned at the decimal place, as is the case when you display a matrix in the command window normally.
Oleg Komarov
Oleg Komarov 2012-6-6
A = randn(3,9);
sprintf([repmat('%10.6f',1,size(A,2)) '\n'],A)
Have you tried it?
You can tweak the %10 to give more space between the numbers.
Jan
Jan 2012-6-6
+1: I still prefer the REPMAT approach. And if the minus character matters, I'd use the '+' specification and replace the '+' by spaces:
A = 1 - randn(3,9); fprintf(strrep(sprintf([repmat('%+10.6f',1,size(A,2)) '\n'],A), '+', ' '));
Anton
Anton 2018-10-10
It seems that this one transposes my matrix in the process though
Stephen23
Stephen23 2018-10-10
编辑：Stephen23 2018-10-10
@Anton: yes, all of the above examples should transpose the array, like this:
fprintf(...,A.')
The fprintf help explains that it "...applies the formatSpec to all elements of arrays A1,... An in column order, and writes the data..." (emphasis added).

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