# Help Defining Variable Contained Within Summation Notation, and Using this Variable for Plot

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Jonathan Pinko on 11 Feb 2020
Commented: Jonathan Pinko on 12 Feb 2020
Hi all,
I am having trouble defining and using a variable in my code. In my code (shown below), I would like to establish a variable "t" that varies from 0 to 1e6, only containing integer values. Therefore, I would like my SumFe56 term to be a function that finds the sum from n=1 to n=1e7 for t=0, and then from n=1 to n=1e7 for t=1, and so on, until my code provides values for SumFe56 from n=1 to n=1e7 for t=1e6. I would then like to use the SumFe56 function in a larger function, BulkFe56, before finally making a plot that shows BulkFe56 values on the y-axis, and t on the x-axis, with the t values varying on this plot from t=0 to t=1e6. Can anyone please tell me the code that would be capable of doing this?
Here is my code, currently:
n = 1:1e7;
t = 0:1e6;
r = .002;
DFe56 = 1e-12;
SumFe56 = sum((1./n.^2).*exp(-n.^2*pi^2*DFe56*t/r^2));
BulkFe56 = (20*.9175)+((6*.9175*(9-20))/pi^2)*SumFe56;
Thanks,
Jonathan

fred ssemwogerere on 11 Feb 2020
Hello, you could use nested for loop. But i envision this running into an "Out of memory" problem sheerly based on the length of "n" and "t".
Jonathan Pinko on 12 Feb 2020
This was a lot of help.
Thank you.