Changing data in excel from NA to a previous number in the column?

I would like to change NA values for tempreature sensors with a previous number in the same column, to make the values consistent. The columns are more than 10000 rows (cells) of reported data, that's why it has to be automated?

Answer 1

[Chaitanya Mallela]

T  = readtable('filename.csv');     % read the file as table
T  = fillmissing(T,'previous');     % fill NaNs with previous values
[r,c] = find(isnan(T{:,:}));        % check remaining NaN present as a first value in the columns

if(~(isempty(r) && isempty(c)))
     T(r,c) = {0};                  % fIll with zeros
end

writetable(T,'filename.csv');       % write the table to file