How can I properly index a table using isnan? (R2020a)

I am writing multiple tables to an Excel spreadsheet, and do not want previously added tables to be overwritten. As such, I have created the following code. The variable R is a 14x11 table completely filled with NaN as my stated readtable range in Excel is currently empty. I have preceding code which uses manually specified filepaths to extract data from files and create the tables.

R = readtable('rangedata.xlsx',...
    'Range','A2:K15',...
    'ReadVariableNames',false)
if isnan(R(1,1))
    writetable(T,'rangedata.xlsx','sheet',1,'Range','A2:B15');
elseif isnan(R(1,4))
    writetable(T,'rangedata.xlsx','sheet',1,'Range','D2:E15');
elseif isnan(R(1,7))
    writetable(T,'rangedata.xlsx','sheet',1,'Range','G2:H15');
else, isnan(R(1,10))
    writetable(T,'rangedata.xlsx','sheet',1,'Range','J2:K15');
end

When running the script, I encounter the error "Check for missing argument or incorrect argument data type in call to function 'isnan'." I have tried changing all my index formatting to the following format, where Var1 is the name of the first variable, but that has not worked either.

if isnan(R(1,{'Var1'}))

[Walter Roberson]

isnan(R{1,1})
isnan(R.Var1(1))
isnan(R{1,'Var1'})

[Ritchie Yu]

Thanks!

Answer 1

[Peng Li]

Either use dot notion or {} pair to access a table element.

Try R.Var1(1) for example.

[Ritchie Yu]

Thank you!