Error for design.alpha(trt = 1:8, k = 2, r = 2)

[SchmidtPaul]

Hi, I just tried to run the following code and received this error:

library(agricolae)

r <- 2
k <- 2
trt <- 1:8

design.alpha(trt = trt, k = k, r = r)
#> Error in `[<-`(`*tmp*`, i, 2, value = alpha[i - 1, 2] + 1): Indizierung außerhalb der Grenzen

^{Created on 2023-01-31 with reprex v2.0.2}

According to the details of the function's documentation we should have case I.

Parameters for the alpha design: I. r=2, k <= s; II. r=3, s odd, k <= s; III.r=3, s even, k <= s-1; IV. r=4, s odd but not a multiple of 3, k<=s
r= replications s=number of blocks k=size of block Number of treatment is equal to k*s

Hence, r = 2 ✔️ and since s = length(trt)/k = 4, we also have k <= s ✔️

As a consequence, we end up in the respective if statement if (r == 2 & k<=s ) (click for permalink to code on github):

        if (r == 2 & k<=s  ) {
            alpha <- matrix(0, nrow = k, ncol = r)
            alpha[2, 2] <- 1
            for (i in 3:k) {
                alpha[i, 2] <- alpha[i - 1, 2] + 1
            }
            serie <- "I"
        }

However, the for statement has a 3:k in it, which - I guess - only works for k >= 3?

So I am not sure - is this intended because r=2 & k=2 is too small? Or what am I missing?

[SchmidtPaul]

Furthermore, it does work in {FielDHub}:

r <- 2
k <- 2
trt <- 1:8

length(trt) / k # = s
#> [1] 4

out <- FielDHub::alpha_lattice(t = length(trt),
                        k = k,
                        r = r)

out
#> Alpha Lattice Design 
#> 
#> Information on the design parameters: 
#> List of 7
#>  $ Reps            : num 2
#>  $ iBlocks         : num 4
#>  $ NumberTreatments: int 8
#>  $ NumberLocations : num 1
#>  $ Locations       : int 1
#>  $ seed            : num 5397
#>  $ lambda          : num 0.286
#> 
#>  10 First observations of the data frame with the alpha_lattice field book: 
#>    ID LOCATION PLOT REP IBLOCK UNIT ENTRY TREATMENT
#> 1   1        1  101   1      1    1     1       G-1
#> 2   2        1  102   1      1    2     3       G-3
#> 3   3        1  103   1      2    1     2       G-2
#> 4   4        1  104   1      2    2     6       G-6
#> 5   5        1  105   1      3    1     8       G-8
#> 6   6        1  106   1      3    2     5       G-5
#> 7   7        1  107   1      4    1     7       G-7
#> 8   8        1  108   1      4    2     4       G-4
#> 9   9        1  201   2      1    1     4       G-4
#> 10 10        1  202   2      1    2     2       G-2

^{Created on 2023-01-31 with reprex v2.0.2}

[Sherry520]

Yes, it works only for k>=3 when r=2.

if (r == 2 & k<=s ) {
alpha <- matrix(0, nrow = k, ncol = r)
alpha[2, 2] <- 1
for (i in 3:k) {
alpha[i, 2] <- alpha[i - 1, 2] + 1
}
serie <- "I"
}

[SchmidtPaul]

Thanks for the reply @Sherry520
So I understand that the code only works for k>=3 when r=2, yes.
But aren't real-life alpha designs possible with r=2 and k=2? I show above that FielDHub can do it. Should the code of {agricolae} not be adjusted?