MATLAB: Reading a table: column name

MATLAB

I created a csv file

morning afternoon
1        0
0        2

I read it using readtable

and then type

morning

then I got

unrecognized function or variable

Please advise.

Best Answer

A column can be read from a table by referring to the the column variable.

data=readtable('filename.csv')

morning=data.morning;

Related Solutions

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: Readtable – renaming variables after creating

See the documentation for Change a Variable Name.

Best Answer

Related Solutions

MATLAB: Table: group by datetime

MATLAB: Readtable – renaming variables after creating

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