how to make an indicator function in loop

Question

Jun Yoo 2020-9-2

编辑： Jun Yoo 2020-9-2

Dear Community,

Hi, im learning Matlab and wondering how to create an indicator function that I can implement in for loop.

for example, y is 10 X 1 array that has "1","2","3" as its values. What I want to do in R version is

for i = 1: length(x)

ll[i] = ifelse(y[i] == 1, 1, 0) * log(p0) + ifelse(y[i]==2,1,0)*log(p1) + ifelse(y[i]==3,1,0)*log(p2)

like if y(i,:) is 1 then 1 else 0 and multiply log(p0) and if y(i,:) is 2 then 1 else 0 and multiply log(p1)

I wanna create another ll and save the caculated values from the loop. is there any nice way to substitute "ifelse" in the calculation?

Answer 1

Alan Stevens 2020-9-2

编辑：Alan Stevens 2020-9-2

You could do the following in Matlab:

   for i = 1:length(x)
   Y = y(i);
   ll(i) = log(p0)*(Y==1) + log(p1)*(Y==2) + log(p2)*(Y==3);
   end

Note that log is log to base e. log10 is log to base 10.