Hello everyone,

restart:with(plots):

xNData := ExcelTools:-Import("D:/a.xls"):

L := convert(xNData, listlist);

L := [[1.0, 0.75e-1], [2.0, .1], [3.0, .12], [4.0, .14], [5.0, .16], [6.0, .18], [7.0, .2], [8.0, .22], [9.0, .24], [10.0, .26]]

In the above L for each x we have N. **I want to sub a single set of value [x,N] into THE equation NN to get a value for d and repeat the same process for each set of [x,N] to get d. **

NN := -N+(N0B-NB)*(erf((1/2)*x/(sqrt(t)*sqrt(d)))-sqrt(erf((1/2)*alpha/d)))/sqrt(erfc((1/2)*alpha/d))+NB;

alpha:=2*10^(-12):NB:=0.075:N0B:=0.2:t:=360000:

Cheers.

@Care Love, sorry for the trouble. I have edited the question.

a.xls