Scott-Knott

[grandonia]

Dears, is there a way to do a Scott-Knott test? I haven´t found a way to do it

[MAgojam]

Hey @grandonia,
if you need a test that jamovi does not yet have available (like the one you are looking for) it is always possible with the Rj module to write some R code to satisfy your needs.
How are you doing with R, do you need help?

Cheers,
Maurizio

[grandonia]

Dear Maurizio, no experience with R Do you know how to implement that in an user friendly way? Thanks so much!!

[MAgojam]

Do you know how to implement that in an user friendly way?

Sorry, but I missed your request.
Here a simplified function that could answer your request, to be copied and pasted in the Rj editor.

Code: Select all

## -- References
# Package: 'ExpDes'
# Version: 1.2.2
# Dates: 2021-10-04
# Authors: Eric Batista Ferreira, Portya Piscitelli Cavalcanti, Denismar Alves Nogueira
# Maintainer: Eric Batista Ferreira

##  Note:
# Changes to the scottknott() function (Multiple comparison: Scott-Knott test)
# for use as an example with jamovi Rj editor.
RjScottKnott <- function(y, x, ResSS, ResDF) {

    skt <- function(medie, s2) {
        prob <- 0.05
        bo <- 0
        si2 <- s2
        defr <- ResDF
        parou <- 1
        np <- length(medie) - 1

        for (i in 1:np) {
            g1 <- medie[1:i]
            g2 <- medie[(i+1):length(medie)]
            B0 <- sum(g1)^2/length(g1) + sum(g2)^2/length(g2) - (sum(g1) + sum(g2))^2/length(c(g1, g2))

            if (B0 > bo) {
                bo <- B0
                parou <- i
            }
        }

        g1 <- medie[1:parou]
        g2 <- medie[(parou+1):length(medie)]
        test <- c(g1, g2)
        sigm2 <- (sum(test^2) - sum(test)^2/length(test) + defr*si2)/(length(test) + defr)
        lamb <- pi*bo/(2*sigm2*(pi-2))
        v0 <- length(test)/(pi-2)
    
        p <- pchisq(lamb, v0, lower.tail=FALSE)
        if (p < prob) {
            for (i in 1:length(g1)){
                cat(names(g1[i]),"\n", file=tmpfile, append=TRUE)
            }
            cat("*","\n", file=tmpfile, append=TRUE)
        }
        
        if (length(g1)>1)
            skt(g1,s2)

        if (length(g2)>1)
            skt(g2,s2)
    }

    medie <- sort(tapply(y, x, mean), decreasing=TRUE)
    rep <- tapply(y, x, length)
    s2 <- ResSS/ResDF/rep[1]
    
    tmpfile <- tempfile(pattern="jamovi", tmpdir=tempdir(), fileext="")
    skt(medie, s2)

    f <- names(medie)
    names(medie) <- 1:length(medie)
    resdf <- data.frame("r"=0, "f"=f, "m"=medie)

    if (file.exists(tmpfile) == FALSE) 
        stop
    else {
        rtab <- read.table(tmpfile)
        file.remove(tmpfile)
        vec <- rtab[[1]]
        vec <- as.vector(vec)
        z <- 1
        
        for (j in 1:length(vec)) {
            if (vec[j] == "*")
                z <- z+1
            
            for (i in 1:length(resdf$f)) {
                if (resdf$f[i]==vec[j]) 
                    resdf$r[i] <- z
            }
        }
    }

    alphabetletters <- letters
    if(length(resdf$r)>26) {
        l <- floor(length(resdf$r)/26)
        for(i in 1:l) 
            alphabetletters <- c(alphabetletters, paste(letters, i, sep=''))
    }

    res <- 1
    for (i in 1:(length(resdf$r)-1)){
        if (resdf$r[i] != resdf$r[i+1]){
            resdf$r[i] <- letters[res]
            res <- res+1
            
            if (i == (length(resdf$r)-1))
                resdf$r[i+1] <- letters[res]

        } else {
            resdf$r[i] <- letters[res]

            if (i == (length(resdf$r)-1)) 
                resdf$r[i+1] <- letters[res]

        }
    }

    names(resdf) <- c("Groups", "Treatments", "Means")
    cat("\nScott-Knott test\n-----------------------------------------\n")
    print(resdf)
    cat('-----------------------------------------\n')

} ## --- End for the Rjscottknott() function.

See the attached screenshot as an example of using the function above with the arguments to modify based on the name of your two variables (data$variablename) and the residual values for SS and DF that you can get from ANOVA in jamovi.

RjScottKnott.png (140.74 KiB) Viewed 1990 times

Cheers,
Maurizio