Loop including 0 R-CodePudding

I create the following range:

x <- seq(0,22)

Now I want to get some expected poisson estimations:

for (val in x) {
  vec[val]<-(dpois(val,6.298387))*124
}

I want also the estimation for val = 0

(dpois(0,6.298387))*124

However, the vector "vec" obtained previously starts at val = 1.

How can I force the loop to take also values = 0?

CodePudding user response：

Since R is 1-indexed, there is no such thing as vec[0]. The first valid index of vec is vec[1], so you probably intended

x <- seq(0,22)

vec <- numeric()

for (val in x) {
  vec[val   1] <- dpois(val, 6.298387) * 124
} 

vec
#>  [1] 2.280694e-01 1.436469e 00 4.523719e 00 9.497378e 00 1.495454e 01
#>  [6] 1.883790e 01 1.977473e 01 1.779270e 01 1.400816e 01 9.803203e 00
#> [11] 6.174437e 00 3.535363e 00 1.855590e 00 8.990174e-01 4.044542e-01
#> [16] 1.698273e-01 6.685238e-02 2.476836e-02 8.666707e-03 2.872962e-03
#> [21] 9.047512e-04 2.713559e-04 7.768656e-05

However, the loop is not necessary, since dpois is vectorized like many R functions. Therefore the above code simplifies to this one-liner:

dpois(0:22, 6.298387) * 124
#>  [1] 2.280694e-01 1.436469e 00 4.523719e 00 9.497378e 00 1.495454e 01
#>  [6] 1.883790e 01 1.977473e 01 1.779270e 01 1.400816e 01 9.803203e 00
#> [11] 6.174437e 00 3.535363e 00 1.855590e 00 8.990174e-01 4.044542e-01
#> [16] 1.698273e-01 6.685238e-02 2.476836e-02 8.666707e-03 2.872962e-03
#> [21] 9.047512e-04 2.713559e-04 7.768656e-05

^{Created on 2022-07-22 by the reprex package (v2.0.1)}