Num2Cell keeps adding onto data array

I'm currently trying to take in multiple files from a directory, do calculations to them, and then save the file to a new directory. The problem I'm having is the num2cell function keeps adding onto the size of the array.

my first iteration

dataf = 9060 x 6

but then my second iteration through

dataf = 9060 x 12

example of a row:

1 2 3 4 5 6 nan nan nan nan nan nan

and this makes it so i cannot combine my matrix's to create the final output.

how do I get rid of the 'nan' issue that occurs.

clear 
clc

[PathName,FileName] = uigetfile({'*.xlsx;*.csv'},'Select Data');

[num txt]=xlsread([FileName,PathName]);

length = size(txt,1);

lengthnum = size(num,1); 

cd('C:\Users\name\Desktop\Stocks_new')

filename = PathName;

dataF = num;
dataF=num2cell(dataF);

title = txt(1,1:7);

dates = txt(2:length,1); 

final = [title; dates dataF];

xlswrite(PathName,final,1)

[KSSV]

Are you sure that the nans are not there in num?