Sorry for the most basic of questions. How would I find the positions of a list of elements which are empty, for example I have the list
a = {1, 2, {}, {}, 3, 5};
and I want to find the indices of the empty elements.
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1 Answer
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If you want to find the position of something in a given expression, you should use Position.
In this example, you could simply write:
Position[{1, 2, {}, {}, 3, 5}, {}]
(*{{3}, {4}}*)
I have to mention that this not the whole power of Position: the second parameter of Position can be a "pattern"(which may be not known by a matlab coder:)), look up the doc for more imformation.
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$\begingroup$ Great thanks, I know a little about regexp $\endgroup$– mor22Commented Jun 13, 2013 at 11:28
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$\begingroup$ @rcollyer Thanks, I'm still learning! $\endgroup$– mor22Commented Jun 14, 2013 at 7:22
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$\begingroup$ Thank you, this is helpful. In some cases, i.e. when importing data, one might need to use {""} instead of {}. $\endgroup$ Commented Sep 13, 2015 at 9:05
Position[{1, 2, {}, {}, 3, 5}, {}]yields{{3}, {4}}$\endgroup${}usingCases[{1, 2, {}, {}, 3, 5}, Except[{}]]. $\endgroup$DeleteCases[{1, 2, {}, {}, 3, 5}, {}]. $\endgroup$