search for: logspace

Displaying 6 results from an estimated 6 matches for "logspace".

Did you mean: argspace
2012 Feb 07
2
predict.naiveBayes() bug in e1071 package
...071:::predict.naiveBayes function takes the probabilities into log-space and adds instead of multiplying probabilities. However, when calculating the posterior probabilities of each class (when type = "raw"), the log of the probabilities are exponentiated, which defeats the purpose of the logspace transformation. I suggest the following change to the code: Towards the end of the predict.naiveBayes function, you currently do: L <- exp(L) L / sum(L) # this is what is returned you can instead use sapply(L, function(lp) {1 / sum(exp(L - lp))}) the above comes from the following equalit...
2019 Jun 24
2
Calculation of e^{z^2/2} for a normal deviate z
>>>>> William Dunlap via R-devel >>>>> on Sun, 23 Jun 2019 10:34:47 -0700 writes: >>>>> William Dunlap via R-devel >>>>> on Sun, 23 Jun 2019 10:34:47 -0700 writes: > include/Rmath.h declares a set of 'logspace' functions for use at the C > level. I don't think there are core R functions that call them. > /* Compute the log of a sum or difference from logs of terms, i.e., > * > * log (exp (logx) + exp (logy)) > * or log (exp (logx) - exp (logy)) > *...
2019 Jun 24
1
Calculation of e^{z^2/2} for a normal deviate z
...mal deviate z >>>>> William Dunlap via R-devel >>>>> on Sun, 23 Jun 2019 10:34:47 -0700 writes: >>>>> William Dunlap via R-devel >>>>> on Sun, 23 Jun 2019 10:34:47 -0700 writes: >> include/Rmath.h declares a set of 'logspace' functions for use at the C >> level. I don't think there are core R functions that call them. >> /* Compute the log of a sum or difference from logs of terms, i.e., >> * >> * log (exp (logx) + exp (logy)) >> * or log (exp (logx) - ex...
2019 Jun 23
0
Calculation of e^{z^2/2} for a normal deviate z
include/Rmath.h declares a set of 'logspace' functions for use at the C level. I don't think there are core R functions that call them. /* Compute the log of a sum or difference from logs of terms, i.e., * * log (exp (logx) + exp (logy)) * or log (exp (logx) - exp (logy)) * * without causing overflows or throwing away too...
2019 Jun 23
2
Calculation of e^{z^2/2} for a normal deviate z
I agree with many the sentiments about the wisdom of computing very small p-values (although the example below may win some kind of a prize: I've seen people talking about p-values of the order of 10^(-2000), but never 10^(-(10^8)) !). That said, there are a several tricks for getting more reasonable sums of very small probabilities. The first is to scale the p-values by dividing the
2019 Jun 24
0
Calculation of e^{z^2/2} for a normal deviate z
...normal deviate z >>>>> William Dunlap via R-devel >>>>> on Sun, 23 Jun 2019 10:34:47 -0700 writes: >>>>> William Dunlap via R-devel >>>>> on Sun, 23 Jun 2019 10:34:47 -0700 writes: > include/Rmath.h declares a set of 'logspace' functions for use at the C > level. I don't think there are core R functions that call them. > /* Compute the log of a sum or difference from logs of terms, i.e., > * > * log (exp (logx) + exp (logy)) > * or log (exp (logx) - exp (logy)) > *...