# How to write this equation?

3 views (last 30 days)
MAHMOUD ALZIOUD on 26 Nov 2019
Commented: MAHMOUD ALZIOUD on 26 Nov 2019
Dear All, I have this equation in excel, what is the best way to write in matlab?
Y = 1.13+13/(1+EXP(7.57-15.5*LOG(x+0.0001)))
I tried this in matlab, but it did not give the same results for all values of x:
Y = 1.13+(13./(1+exp(7.57-15.5.*log(x+0.0001))));
x is a vector column of 200 values.

Image Analyst on 26 Nov 2019
What values did x cover? Which of those gave a different value? Can you attach x in a .mat file or .xlsx file?
MAHMOUD ALZIOUD on 26 Nov 2019
Yes now this is the file, please see the columns of the results.
thanks

Rik on 26 Nov 2019
There is a difference between log and log10. What you have done in Excel is actually calculate the log10, because you omitted the base as an input. The log function in Matlab computes the natural logarithm. If you want to have the same effect, either put EXP(1) as the base in Excel, or use this in Matlab:
Y = 1.13+(13./(1+exp(7.57-15.5.*log10(x+0.0001))));

#### 1 Comment

MAHMOUD ALZIOUD on 26 Nov 2019
Amazing, thank you very very much