How can I delete/extract rows from a table with cell columns consisting of str and numeric values

Question

Peter Jaenicke 2017-7-14

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评论： Peter Perkins 2017-7-18

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I have a table comprising of number and cell columns:

From this table I would like to extract all rows which have "pits" in a cell in column 3 / Type.

My approaches so far:

1. Extract it via "strfind"

Ppits=P(cellfun(@isempty, strfind(P.Type, 'pits')), :);

Error:

Error using strfind
Cell must be a cell array of character vectors.

2. Delete rows with "0" or []. All attempts like logical indexing didn't work due to the fact that it's a table or the column has numerical and str values.

e.g.

>> toDelete = P < 6;
P(toDelete,:) = [];
Undefined operator '<' for input arguments of type 'table'.

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Peter Perkins 2017-7-18

Change the zeros to ''. Those elements will become undefined categorical values.

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Answer 1

dbmn 2017-7-14

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The easiest way to extract the "pits" is to do the following

% Convert your column type to a format called categorical
% This format is supported by the table format
  P.Type = categorical(P.Type)
% Then you can compare it like you would with numbers
  P(P.Type == 'pits', :)

if you want to do the same with f.ex PH value just use

P(P.pH < 7, :)

and combine the two as you like

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Peter Jaenicke 2017-7-14

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First of all, thank you for your answer. Using

P.Type = categorical(P.Type)

results into

Error using categorical (line 347)
Could not find unique values in DATA using the UNIQUE function.
Caused by:
    Error using cell/unique (line 85)
    Input A must be a cell array of character vectors.