How do we count non-zero entries in every column in a table?
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ahmed obaid
on 29 Mar 2017
Commented: ahmed obaid
on 31 Mar 2017
Dear experiences
i have a sparse matrix stored in an excel file, i read this matrix using (read table), i need to count every non-zero entries in every column and remove columns that do not satisfy condition (like K where k=3) such that remove columns that involve 1 and 2 non-zero entries and saved others. note: when columns are removed must be removed along with its header or "title" information using Matlab 2015?
thanks for any participation ...
Accepted Answer
Andrei Bobrov
on 30 Mar 2017
Let T - your table:
x = [0 0 193 0 0 0 37 0;
53 0 0 0 0 0 0 0;
0 161 0 0 0 0 0 0;
0 0 47 160 0 0 6 15;
0 186 98 0 0 0 0 0;
0 147 125 53 0 0 34 0;
0 0 0 0 0 0 196 0;
0 0 0 0 0 0 143 164;
0 0 0 0 0 0 101 0;
102 92 0 145 0 0 0 0];
xc = num2cell(x,1);
T = table(xc{:},'VariableNames',cellstr(strcat(string('column_'),string(1:numel(xc)))));
k = 3;
t = varfun(@(x)sum(x~=0),T ,'OutputFormat','uniform');
% or t = sum(T{:,:} ~= 0);
out_table = T(:,t >= k);
3 Comments
Andrei Bobrov
on 31 Mar 2017
x = readtable('c.xls')
k = 3;
y = x(:,2:end);
t = sum(y{:,:} ~= 0);
out_table = [x(:,1),y(:,t >= k)];
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