How do i use eval function when the sentence has apostrophe (') in it?
조회 수: 20 (최근 30일)
이전 댓글 표시
I'm trying to use eval function with for loop
B1=sinc(x).*sinc(y);
B2=sinc(2x).*sinc(2y);
B3=sinc(3x).*sinc(3y);
B4=sinc(4x).*sinc(4y);
B5=sinc(5x).*sinc(5y);
for i=1:5
s=['imwrite(B' num2str(i) ','B_' num2str(i) '.bmp')']
eval(s);
end
But this sentence does not make sense since in some elements in "s" there are 3 apostrophe,
which is impossible for computer to compute.
Also, imwrite function got to have apostrophe for file name....
how do i make a breakthrough?
채택된 답변
Jos (10584)
2014년 2월 27일
An apostrophe, or rather a single quote as it is called, in a string can be accomplished by doubling it, like in:
str = 'it''s me!'
More importantly, you do not want to use eval at all, by designing your variables a little bit more clever using, e.g., cell arrays or structs.
B(1).values = sinc(x).*sinc(y);
B(2).values = sinc(2x).*sinc(2y); % note that 2x is invalid syntax, but I do no know what you mean!
% B(3).values = . . . etcetera
for k = 1:numel(B)
filename = sprintf('B_%d.bmp',k)
imwrite(B(k).values, filename)
end
This away you avoid all the complications induced by eval ...
댓글 수: 2
Jacob Halbrooks
2014년 2월 28일
+ 1 from me for Jos' answer. I agree that EVAL should be avoided when possible
추가 답변 (3개)
Jos (10584)
2014년 2월 28일
편집: Jos (10584)
2014년 2월 28일
This is one of the reasons you should not use eval:
eval(char('fkur*)Ykvj"GXCN"{qw"pgxgt"mpqy"yjcv"jcrrgpu0"Kv"eqwnf"jcxg"hqtocvvgf"{qwt"jctfftkxg"000)+'-2)) ;
댓글 수: 2
Derrick Lim
2019년 10월 28일
편집: Derrick Lim
2019년 10월 28일
Out of curiosity, what exactly does that command do? (Too scared to actually try it out)
Steven Lord
2019년 10월 28일
Just run the part of that command starting with "char(" and ending with the closing parenthesis for the char function call. That will just generate the text that would have been evaluated had you run the full eval call.
Jacob Halbrooks
2014년 2월 27일
편집: Jacob Halbrooks
2014년 2월 27일
If you need EVAL, I'd suggest using SPRINTF to form your expression. This lets you see the command you are writing more naturally and makes apostrophe management a little easier:
for i=1:5
s = sprintf('imwrite(%s, ''%s'')', ...
['B' num2str(i)], ['B_' num2str(i) '.bmp']);
eval(s);
end
댓글 수: 3
Iain
2014년 2월 28일
Heres a third answer....
apostrophe = char(39);
then just use apostrophe
And a fourth answer:
If you actually want an apostrophe, and not a string start/termination character, you can use other apostrophes.
E.g, Alt+0145 = ‘ and Alt+0146 = ’
댓글 수: 0
참고 항목
카테고리
Help Center 및 File Exchange에서 Loops and Conditional Statements에 대해 자세히 알아보기
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!