how to combine strfind and index in one line？

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raym
raym 2017-3-3
编辑： Walter Roberson 2017-3-3
I tried to run strfind(argument,argument)(1) to return the first hit position, but matlab returns a error. It seems that I need to split the command into two lines？ right？Is there any other way to make it in one line？

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Walter Roberson
Walter Roberson 2017-3-3
second_last = @(V) V(end-1);
positionLast2nd = second_last(strfind(newname, '_'));
It is possible to do it without the helper function, but it really is not worth doing except to prove that you can, because the code gets obscure.

更多回答（2 个）

Chad Greene
Chad Greene 2017-3-3
编辑：Chad Greene 2017-3-3
You could use regexp with the 'once' option. For example, for this string:
str = ['Soldiers! Don''t give yourselves to brutes - men who despise you, enslave you, who '...
'regiment your lives, tell you what to do, what to think or what to feel! Who drill you,'...
'diet you, treat you like cattle, use you as cannon fodder.']
Each instance of the word you begins at the following indices:
regexp(str,'you')
ans =
22 61 74 92 109 166 176 187 208
If you only want the first instance use the 'once' option:
regexp(str,'you','once')
ans =
22
  2 个评论
raym
raym 2017-3-3
编辑：Walter Roberson 2017-3-3
Hi,Chad.
Thanks a lot.
Dose regexp has other options to retrieve other than the first position?
In fact this is what I really want to do:
newname = 'aasw_43w-f45_rmg-rk_dwfewf_rgrg_v-b';
nich = strfind(newname,''_'');
% find the position of last second '_':
positionLast2nd = nich(length(strfind(newname,''_''))-1)
=====
I tried to combine these two commands in one line as:
positionLast2nd = strfind(newname,''_'')(length(strfind(newname,''_''))-1)
error appears.

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raym
raym 2017-3-3
编辑：Walter Roberson 2017-3-3
newname = 'aasw_43w-f45_rmg-rk_dwfewf_rgrg_v-b';
eval('nich = strfind(newname,''_''); nich(length(strfind(newname,''_''))-1)')
% ans then could be used directly.
  1 个评论
Walter Roberson
Walter Roberson 2017-3-3
We distinctly recommend against using eval. eval() often leads to subtle bugs that show up only sometimes and are hard to find. It is also a big security risk.

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