I am trying to reproduce the example of Data Cleaning from here. I had to make a slight change in input 13 to

j[x_] := If[StringMatchQ[x, "TOTAL*"], x, DateList[x]];

After running input 14 I get the following data:


There is a TOTAL row for every year. The article proposes to delete those rows by running (asterisk is my contribution)

tmp4 = DeleteCases[tmp3, {"TOTAL*", __}];

but it doesn't work! After searching StackExchange, I found that DeleteCases is not compatible with string patterns.

So how do we delete those rows? And if DeleteCases is truly incompatible, how did the Mathematica article succeed?

PS: I did manage to delete those rows by sorting the data and dropping them, but I'd still like to know how to do it with DeleteCases.




1 Answer 1


Using a simpler example

tmp3 = {{"TOTAL*", 1, 2}, {"TOTAL123", 1, 2}, {a, b, c}};

Your code deletes only the first element in which the first entry literally matches "TOTAL*"

DeleteCases[tmp3, {"TOTAL*", __}]
{{"TOTAL123", 1, 2}, {a, b, c}}

To get the desired result you need to specify the first element of list in the pattern to be matched as a String which StringMatches the string pattern "TOTAL*". You can do this using PatternTest (?) or using Condition (/;):

DeleteCases[tmp3, {_String?(StringMatchQ[#, "TOTAL*"] &), __}] (* or *)
DeleteCases[tmp3, {s_String /; StringMatchQ[s, "TOTAL*"], __}]

{{a, b, c}}


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