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Dear list! I work with multiple Kruskal-Wallis test (kruskalmc, package pgirmess), which evaluates differences in medians among groups (5 groups). A result of a test is significant differences among some groups, while median values are the same for 4 groups (using tapply). Why? p.s.: number of samples in groups vary from 50 to 4900. Thanks to all, OV .

Dear list! I would like to calculate "chisq.test" on simple data set with 70 observations, but the output is ''Warning message:'' Warning message: In chisq.test(tabele) : Chi-squared approximation may be incorrect Here is an example:         tabele <- matrix(c(11, 3, 3, 18, 3, 6, 5, 21), ncol = 4, byrow = TRUE)         dimnames(tabela) <- list(        

Dear list!   I would like to write a function to transform matrix, which is input argument of a written function. It is easy with new matrix (see below), but my idea is to transform input argument (matrix) of function without any additional matrixes. Here is an example: fun1 <- function(xy) { xy <- cbind(xy[,1], xy[,2], xy[,1] + xy[,2]) return(xy) }   df1 <- matrix(c(1,2,3,1,2,3), ncol =

Dear list members! I am looking for ''nice solution'' for (maybe) simple problem. I need a code (small program) to calculate row index for max value (example below: df1$values) by groups (example below: df1$groups). df1 <- data.frame( groups = c(1,1,1,1,1,2,2,2,3,3,3,3), values = c(1,1,1,2,1,1,2,3,2,1,4,3) ) df1 expected results > 4 8 11 # row index of max values by group

Dear list! I have problem with buffer size (width) in package rgeos. I would like to expand given geometry (points) to specified width based on the z value from attribute table. Here is example: point <- data.frame(x=c(10,20), y=c(10, 10), z = c(2,7)) point_shp <- SpatialPointsDataFrame(point[,1:2],point) plot(point_shp, xlim = c(0,30), ylim = c(0,20)) plot(gBuffer(point_shp, width = 5,

Dear list! ? I have question of?'correct function formation'. Which function (fun1 or fun2; see below) is written more correctly? Using ''structure'' as output or creating empty ''data.frame'' and then transform it as output? (fun1 and fun1 is just for illustration). ? Thanks a lot, OV ? code: input <- data.frame(x1 = rnorm(20), x2 = rnorm(20), x3 =

Hi everybody! I have a matrix of class "myClass", for example: myMat <- matrix(rnorm(30), nrow = 6) attr(myMat, "class") <- "myClass" class(myMat) When I extract part of ''myMat'', the corresponding class ''myClass'' unfortunately disappear: myMat.p <- myMat[,1:2] class(myMat.p) Please for any advice / suggestions, how

Hi R-helper! I have problem with setMethods for "[". Here is example : setClass("myClass", representation(ID.r = "numeric", ID.c = "character", DAT = "matrix")) to.myClass <- function(ID.r, ID.c, DAT) {     out <- new("myClass", ID.r = ID.r, ID.c = ID.c, DAT = DAT)     return(out)       }       setMethod("[",

Hi all!   My question is how to colour pixels by z value in persp plot in raster package. Here is an example:     x <- seq(-1.95, 1.95, length = 30) y <- seq(-1.95, 1.95, length = 35) z <- outer(x, y, function(a,b) a*b^2) r1 <- raster(nrows=35, ncols=30, xmn=0, xmx=30, ymn = 0, ymx = 35) r1[] <- c(z) persp(r1)   There already exist some function to produce persp plot for anothe

Dear R helpers! I have a vector 'x1' and data.frame 'df1'. Do you have any suggestion how to get vector x2, which will be a result of matching values from vector 'x1' and values from 'df1'? Please, see the example: x1 <- c(rep(1,3), rep(NA,2), rep(2,4)) df1 <- data.frame(c1 = c(1,2), c2 = c(5,6)) I would like to get vector x2: > x2 [1]  5  5  5 NA NA  6 

Hi all!   My question in about using mapply instead for loop. Below is a example with for loop: Is it posible to give same results with mapply function?   Thanks for help!   OV   x <- 1:10 y <- 1:10 xyz <- data.frame(expand.grid(x,y)[1], expand.grid(x,y)[2], z = rnorm(100)) names(xyz) <- c("x", "y", "z") head(xyz) size <- 2 output <- NULL   ### for