How can I extract data with respect to certain non numeric values

I have a csv file, which have numeric and non numeric columns. e.g the first, second and fourth column has numbers and the third column has letters i.e C,S,CA. I have imported the file and sorted the third (non-numeric) column so all the C, CA and S values are listed together. How can I extract rows of data that are associated with 'CA'? Thanks

Answer 1

[Image Analyst]

Use readtable() to read your data into a table. Then use ismember() to find out which rows have CA in them, then use that to filter the rows. If you don't understand, then attach your data (csv file).

[shellmcg]

Thanks Image Analyst Yes I am a bit confused so Please find attached a small part of the data set. I would like to import the file into Matlab and extract all the rows related to the CA atom and store that data in a separate matrix. Thanks again

[Image Analyst]

Try this:

t = readtable('sample data.csv')
% Extract column 2 only
col2 = t.atom_types
% Find out which rows in column 2 are 'CA'
caRows = ismember(col2, 'CA')
% Extract those rows ONLY into a new table.
caRowsInTable = t(caRows, :)

The final result:

caRowsInTable = 
    atom_type    atom_types    residue    chain    secondary_structures    secondary_structures_begin
    _________    __________    _______    _____    ____________________    __________________________
    5            'CA'          1          32       99                       39                       
    5            'CA'          1          32       99                        0                       
    5            'CA'          2          32       99                       40                       
    5            'CA'          2          32       99                        0                       
    5            'CA'          3          32       99                      125

[shellmcg]

Thanks Image Analysis. I am getting an error with readtable function 'Undefined function 'readtable' for input arguments of type 'char'. I have loaded my data but I seem to be missing the column names so if I wanted CAs out of column 2 could I use col2=t.(:,2) instead of col2 = t.atom_types? Cheers

[shellmcg]

Thanks Image Analysis. It worked!!

Answer 2

[Yuebin Zhou]

You can check the link below:

http://stackoverflow.com/questions/8061344/how-to-search-for-a-string-in-cell-array-in-matlab

[shellmcg]

Thanks Yuebin but I actually want to store all the data in the CA rows in a separate matrix