MATLAB: How to write log base e in MATLAB

Question

I have attached a picture of what i am trying to type in MATLAB. I get an error when i put loge(14-y), so im assuming im typing it wrong and MATLAB cannot understand what i am looking for. Any help would be great, Thank you

Answer 1

The log function does exactly what you want.

log(14 - y)

If you want a base 10 log, you use log10. There is also a log2 function, which gives a base 2 log. Other bases are achieved using the simple relation

log(X)/log(b)

produces a log to the base b. You could write a function for it as:

logb = @(X,b) log(X)/log(b);
logb(9,3)
ans =
                         2

which is as expected.

Finally, there is the reallog function, which also does the natural log, but it produces an error when the log would have been a complex number.

log(-2)
ans =
          0.693147180559945 +      3.14159265358979i
          
reallog(-2)
Error using reallog
Reallog produced complex result. 

But for the more normal case, reallog does the same thing as log.

log(2)
ans =
         0.693147180559945
reallog(2)
ans =
         0.693147180559945