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I'm an intermediate Mathematica user and the select function presented on Data Table Manipulation in Mathematica: Step 2 was very useful in helping me manipulate a 36Mb data file - 13 columns and 180k rows. The challenge I'm having is writing a similar function that will remove rows based on selected column entities, returning the subset of data as a new data table. Any assistance will be appreciated. Thanks.

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closed as unclear what you're asking by Yves Klett, Öskå, Mr.Wizard Jun 21 '14 at 19:50

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

Welcome to Mathematica StackExchange. Is there any reason that you can't simply logically negate your where condition? E.g. select[data, where["col" == val]] -> select[data, where[Not["col" == val]]]. If you post some example code you might get more help! –  MikeLimaOscar Jun 20 '14 at 16:57
Some clarification. Do you want to select columns for removal by specifying their headings (likely a string, as in the posting at the link), by their column number, or by virtue of having data values meeting some criterion? –  user15996 Jun 20 '14 at 16:58
your question is not clear what do you mean by column entities. are these entities indices of row (number of rows) or just any entities?. based on your question, you have a list of dimension 180K by 13. each column will has 180k entities so if you are going to delete one raw per one column entities then all rows are going to be deleted. –  Algohi Jun 20 '14 at 21:01
Please clarify your question and explain your terminology. A short toy input/output example would be helpful. –  Yves Klett Jun 21 '14 at 16:14

1 Answer 1

From what I can tell MikeLimaOscar is spot on; you just need to negate your where condition so that instead of selecting what you want to remove, you select what you don't want to remove. Your link points to "step 2" which is the wrong method for what you want to do though, you should be looking at the first step, available here.

For example, to remove all rows where ID == "Beta":

select[table, where["ID" != "Beta"]]
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