for loop - Summation of max function with vector input in R? -


i want build function: f(a,b)=sum_{i=1 n}(max(a-b_i,0)) b=(b_1,b_2,...b_n). have done: 

    vec<-function(a,b){                   z<-0                    for(i in b){                          ifelse(a > i,z <- z + (a-i), 0)                        }                 return(data.frame(z))                    }

this code gives correct output scalar input of a. while using vector output answers not correct. example 

    > vec(c(-6,5),c(3,1,3))    gives -25 a=-6 , 8 a=5 respectively.      > vec(-6,c(3,1,3))  gives 0. , correct answer.

please throw give idea how correct it.

when let a = c(-6,5), argument a > i becomes (false, true). since contains true, vector passed z <- z + (a-i). note if use a=-6 in formula, output of -25. suggest doing this: 

vec<-function(a,b){ z<-0 for(i in b){ p <- ifelse(a > i,z <- z + (a-i), 0) } return(data.frame(p)) }

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