Hi, Thanks for ur reply! I also tried that, but as I mentioned the value is very sensitive as x tends to 1 or -1 , ! so if u try for .9999999 we can see drastic change, ! but as for .999....9(fifteen 9s) its value is around 18.57 , after that it becomes inf. so i approximated the value to that .999....9. with a little error. anyhow i solved the problem , thanks for giving inputs! Best Regards, -SaiRamesh. --- V Ravi Chander <> wrote: > > Hi again! > I dont know what is the step size that you are using > for x. > I tried this in MATLAB > > atanh(0.999999) > > ans = > > 7.25432861924767 > > so even if you have a step size as small as > 0.000001, the value doesn't > really shoot up for the value of x just before 1 or > -1. > > You can approximate the value at (x = 1) to 10 (or > whatever you think is > suitable in your work). > > regards, > Ravi > > > > > > Hi, > > Thanks for your reply! It is obvious that it > will > > give inf when x= 1. I asked in this type of cases, > > how to tackle the problem in Matlab, I can not > > approximate as the graph of atanh(x)is very > sensitive > > as x close to 1 or -1. My algorithm has to use > > atanh(x). Any help in this regard in MATLAB is > highly > > appreciated. > > Regards, > > -SaiRamesh. > > > > > > > > > > > > --- wrote: > > > >> Let us look at the formula for hyperbolic tan > >> inverse > >> > >> arctanh(x) = 0.5 * log ((1+x)/(1-x)) > >> > >> Substituting the value of x as 1 or -1, you would > >> expect to get some wierd > >> answer, isn't it? > >> > >> > >> > > >> > > >> > > >> > Hi, > >> > I am implenting a turbo decoder for a > channel > >> coding scheme. In > >> > that I have to implement a SISO(Soft Input Soft > >> Output) decoder for my > >> > system. In SISO, I have to compute > loglikelihood > >> ratios which > >> > invloves formulas involving arctanh(x). I am > >> facing the problem when x= > >> > 1 or -1 then matlab is giving me inf and -inf > >> respectively and it is > >> > giving erroroneous result. > >> > Any help in this regard is highly appreciated. > >> > > >> > Best Regards, > >> > -SaiRamesh. > >> > > >> > > >> > > >> > > >> > > >> > > >> > > >> > > >> > ------------------------ Yahoo! Groups Sponsor > >> > > >> > _____________________________________ > >> > Note: If you do a simple "reply" with your > >> client, only the author > >> > of this message will receive your answer. You > >> need to do a "reply all" > >> > if you want your answer to be distributed to > the > >> entire group. > >> > > >> > _____________________________________ > >> > About this discussion group: > >> > > >> > To Join: > >> > > >> > To Post: > >> > > >> > To Leave: > >> > > >> > Archives: > http://www.yahoogroups.com/group/matlab > >> > > >> > More DSP-Related Groups: > >> http://www.dsprelated.com/groups.php3 > >> > Yahoo! Groups Links > >> > > >> > > >> > > >> > > >> > > >> > >> > >> -- > >> V Ravi Chander, > >> Research Engineer, > >> Emerging Technologies and Services Group, > >> Reliance Infocomm Ltd. > >> > >> > >> > > > > > > > > > > _______________________________ > > > > > > > > > > > > > > _____________________________________ > > Note: If you do a simple "reply" with your email > client, only the author > > of this message will receive your answer. You > need to do a "reply all" > > if you want your answer to be distributed to the > entire group. > > > > _____________________________________ > > About this discussion group: > > > > To Join: > > > > To Post: > > > > To Leave: > > > > Archives: http://www.yahoogroups.com/group/matlab > > > > More DSP-Related Groups: > http://www.dsprelated.com/groups.php3 > > Yahoo! Groups Links > > > > > > > > -- > V Ravi Chander, > Research Engineer, > Emerging Technologies and Services Group, > Reliance Infocomm Ltd. > _______________________________ |