I'm a novice at matlab so I apologize if this is a dumb question: I need to find the sum of A, B and C given X, Y and Z, where ln(A)=X, ln(B)=Y etc. However, the values A, B and C are so small that when I try to use 'exp' the result is rounded to zero. This is a problem because later in my code I divide sum(A,B & C) by a number, take the log of the result and multiply this by another number as part of a loglikelihood equation. Obviously, since you cannot take the log of 0 this rounding poses a problem for my code. this part of the code is trying to find the binomial coefficient, and I can do the task with nchoosek and vpi but it slows down the code to the point that it is unusable(I'm plugging the code into fminsearch to optimize parameters, and the search takes days or cuts itself off after a time). I've tried just adding logs of numbers and subtracting the same amount later so that exp doesn't get tripped up, but I'm now faced with a situation where that doesn't work.(adsbygoogle = window.adsbygoogle || []).push({});

v=(X+Y)+z;

g=exp(v); %This is where the numbers get rounded to zero

D=sum(g);

gg=log(D); %log(0) gets turned to -Inf, cause the code to not work.

Any advice would be appreciated.

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Matlab, logarithms and rounding small numbers to zero

Loading...

Similar Threads for Matlab logarithms rounding |
---|

MATLAB MATLAB: forces acting on an object |

MATLAB Matlab histogram |

MATLAB Sovling Bernoulli's differential equation in matlab? |

MATLAB Matlab-like software |

MATLAB Matlab data into bins |

**Physics Forums | Science Articles, Homework Help, Discussion**