MATLAB: Table: Delete rows that contain only zeros

deleteMATLABrowstablezeros

Hi,

I am new to Matlab, but I could not find a solution after a lot of searching. I am trying to erase all rows that contains only zeros in a table (for instance row "topics 1").

I am using a table so I keep the "names" of the rows that should not be deleted for later use.

I am using Matlab Version R2020b.

The original table is attached.

Can anybody help?

Thanks in advance!

Best Answer

mask = all(T{:,2:end}==0,2);
T(mask,:) = [];

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MATLAB: Table: group by datetime

It isn't possible. To illustrate, I'll sum by matching date (instead of hour) using datetime versus datenum.

VALUE=[2;3;4];
dt = datetime(2015,[1;2;1],1);
tbl_dt=table(dt,VALUE,'VariableNames',{'dt','VALUE'});
tbl_dt=varfun(@nansum,tbl_dt,'GroupingVariables',{'dt'});

MATLAB returns

Error using table/varfun (line 154)
A grouping variable must be a categorical, numeric, or logical vector, a cell vector of strings, or a 2D character array.

Now use datenum instead:

dn = datenum(2015,[1;2;1],1);
tbl_dn=table(dn,VALUE,'VariableNames',{'dn','VALUE'});
tbl_dn=varfun(@nansum,tbl_dn,'GroupingVariables',{'dn'});

Because datenum is an integer, MATLAB has no problem:

tbl_dn = 
                    dn        GroupCount    nansum_VALUE
                __________    __________    ____________
      735965    7.3597e+05    2             6           
      735996      7.36e+05    1             3

If you have table variables with dates or times and need to do grouping or summary functions (i.e. varfun or grpstats), this makes datetime pretty much useless. You could work around it by casting the value from datetime to datenum around each operation. Perhaps there is a forthcoming modification to varfun that would solve this limitation.

MATLAB: Table: Add only selected collumns

1. Create the full table first, however you were going to create it:

name = {'Joe'; 'Elisa'; 'John'};
age = [30; 10; 25];
weigth = [100; 150; 180];       %note that weigth is mispelled, should be weight
t = table(name, age, weight)

2. use logical indexing to select the columns you want:

selected = [1, 0, 1];
selected = logical(selected); 
%or create it directly as logical:
%selected = [true, false, true];
filteredtable = t(:, selected)  %only keep selected columns

Best Answer

Related Solutions

MATLAB: Table: group by datetime

MATLAB: Table: Add only selected collumns

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