diff --git a/NAMESPACE b/NAMESPACE
index a319f567d56eaff446cd2a706ab118a5bae1ae17..3aa0e32d49da4bd96cef708c8736ebc94eccb765 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -28,6 +28,7 @@ export(MultiEOF)
 export(PlotCombinedMap)
 export(PlotForecastPDF)
 export(PlotMostLikelyQuantileMap)
+export(PlotTriangles4Categories)
 export(RFSlope)
 export(RainFARM)
 export(SplitDim)
diff --git a/NEWS.md b/NEWS.md
index f108f5db59e4223372e2c4917de88e00ab23618d..f81ad72009e66668673cf8c4f8f2bde9ba029386 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -6,6 +6,7 @@
     + EnsClustering has a new parameter 'time_dim'
     + CST_BiasCorrection has na.rm paramter
     + CST_Anomaly allows to smooth the climatology with filter.span parameter
+    + PlotTriangles4Categories new plotting function to convert any 3-d numerical array to a grid of coloured triangles.
 - Fixes
     + CST_Anomaly handles exp, obs or both
     + PlotForecastPDF vignette displays figures correctly
diff --git a/R/PlotTriangles4Categories.R b/R/PlotTriangles4Categories.R
new file mode 100644
index 0000000000000000000000000000000000000000..cda320f9a71b7ac0a32a3dfb3821e8f931f3cb9e
--- /dev/null
+++ b/R/PlotTriangles4Categories.R
@@ -0,0 +1,286 @@
+#'Function to convert any 3-d numerical array to a grid of coloured triangles. 
+#'
+#'This function converts a 3-d numerical data array into a coloured 
+#'grid with triangles. It is useful for a slide or article to present tabular results as 
+#'colors instead of numbers. This can be used to compare the outputs of two or four categories (
+#'e.g. modes  of variability, clusters, or forecast systems). 
+#'
+#'@param data array with three named dimensions: 'dimx', 'dimy', 'dimcat', 
+#'  containing the values to be displayed in a coloured image with triangles.
+#'@param brks A vector of the color bar intervals. The length must be one more 
+#'  than the parameter 'cols'. Use ColorBar() to generate default values.
+#'@param cols A vector of valid colour identifiers for color bar. The length
+#'  must be one less than the parameter 'brks'. Use ColorBar() to generate 
+#'  default values.
+#'@param toptitle A string of the title of the grid. Set NULL as default.   
+#'@param sig_data logical array with the same dimensions as 'data' to add layers 
+#'  to the plot. A value of TRUE at a grid cell will draw a dot/symbol on the 
+#'  corresponding triangle of the plot. Set NULL as default.
+#'@param pch_sig symbol to be used to represent sig_data. Takes 18 
+#' (diamond) by default. See 'pch' in par() for additional 
+#' accepted options.
+#'@param col_sig colour of the symbol to represent sig_data. 
+#'@param cex_sig parameter to increase/reduce the size of the symbols used 
+#'  to represent sig_data.
+#'@param xlab A logical value (TRUE) indicating if xlabels should be plotted
+#'@param ylab A logical value (TRUE) indicating if ylabels should be plotted
+#'@param xlabels A vector of labels of the x-axis The length must be 
+#'  length of the col of parameter 'data'. Set the sequence from 1 to the 
+#'  length of the row of parameter 'data' as default.
+#'@param xtitle A string of title of the x-axis. Set NULL as default.
+#'@param ylabels A vector of labels of the y-axis The length must be 
+#'  length of the row of parameter 'data'. Set the sequence from 1 to the 
+#'  length of the row of parameter 'data' as default. 
+#'@param ytitle A string of title of the y-axis. Set NULL as default.
+#'@param legend A logical value to decide to draw the color bar legend or not. 
+#'  Set TRUE as default.
+#'@param lab_legend A vector of labels indicating what is represented in each 
+#'category (i.e. triangle). Set the sequence from 1 to the length of 
+#' the categories (2 or 4).  
+#'@param cex_leg a number to indicate the increase/reductuion of the lab_legend used 
+#'  to represent sig_data.
+#'@param col_leg color of the legend (triangles).
+#'@param fileout A string of full directory path and file name indicating where 
+#'  to save the plot. If not specified (default), a graphics device will pop up. 
+#'@param size_units A string indicating the units of the size of the device 
+#'  (file or window) to plot in. Set 'px' as default. See ?Devices and the 
+#'  creator function of the corresponding device.
+#'@param res A positive number indicating resolution of the device (file or window) 
+#'  to plot in. See ?Devices and the creator function of the corresponding device.
+#'@param ... The additional parameters to be passed to function ColorBar() in 
+#'  s2dverification for color legend creation.
+#'@return A figure in popup window by default, or saved to the specified path.
+#'
+#'@author History:\cr
+#'1.0  -  2020-10  (V.Torralba, \email{veronica.torralba@bsc.es})  -  Original code
+#'
+#'@examples 
+#'#Example with random data
+#' arr1<- arr1<- array(runif(n = 12 * 7 * 4, min=-1, max=1),dim = c(12,7,4))
+#' names(dim(arr1)) <- c('dimx','dimy','dimcat')
+#'arr2<- array(TRUE,dim = dim(arr1))
+#'arr2[which(arr1 < 0.3)] = FALSE
+#'PlotTriangles4Categories(data = arr1,
+#'                   cols = c('white','#fef0d9','#fdd49e','#fdbb84','#fc8d59',
+#'                            '#e34a33','#b30000', '#7f0000'),
+#'                   brks = c(-1, 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 1), 
+#'                   lab_legend = c('NAO+', 'BL','AR','NAO-'), 
+#'                   xtitle = "Target month", ytitle = "Lead time",
+#'                   xlabels = c("Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul",
+#'                               "Aug", "Sep", "Oct", "Nov", "Dec"))
+#'@importFrom grDevices dev.new dev.off dev.cur 
+#'@export
+
+PlotTriangles4Categories <- function(data,cols=NULL,brks=NULL,
+                                     toptitle=NULL,
+                                     sig_data=NULL,col_sig='black',pch_sig=18,
+                                     cex_sig=1,
+                                     labx=TRUE, 
+                                     laby=TRUE, 
+                                     xlabels=NULL, xtitle=NULL, 
+                                     ylabels=NULL, ytitle=NULL,
+                                     legend=TRUE,lab_legend=NULL,
+                                     cex_leg=1,col_leg='black',
+                                     fileout=NULL,
+                                     size_units = 'px', res = 100,
+                                     figure.width = 1,
+                                     ...){
+  # Checking the dimensions
+  if (length(dim(data))!=3) {
+    stop("Parameter 'data' must be an array with three dimensions.")
+  }
+  
+  if (any(is.na(data))){
+    stop("Parameter 'data' cannot contain NAs.")
+  }
+  
+  if (is.null(names(dim(data)))) {
+    stop("Parameter 'data' must be an array with named dimensions.")
+  }else{
+    if (!any(names(dim(data))=='dimx')|!any(names(dim(data))=='dimy')|!any(names(dim(data))=='dimcat')){
+      stop("Parameter 'data' should contain 'dimx', 'dimy' and 'dimcat' dimension names. ")
+    }
+  }
+  
+  if (!is.null(sig_data)) {
+    if (!is.logical(sig_data)) {
+      stop("Parameter 'sig_data' array must be logical.")}
+    else if (length(dim(sig_data)) !=3) {
+      stop("Parameter 'sig_data' must be an array with three dimensions.")
+    }else if (any(dim(sig_data) != dim(data))){
+      stop("Parameter 'sig_data' must be an array with the same dimensions as 'data'.") 
+    }else if(!is.null(names(dim(sig_data)))){
+      if (any(names(dim(sig_data)) != names(dim(data)))){
+        stop("Parameter 'sig_data' must be an array with the same named dimensions as 'data'.")}
+    }
+  }
+
+  if (dim(data)['dimcat'] != 4 && dim(data)['dimcat'] != 2) {
+    stop(
+      "Parameter 'data' should contain a dimcat dimension with length equals
+      to two or four as only two or four categories can be plotted.")
+  }      
+  
+  # Checking what is available and generating missing information 
+  if (!is.null(lab_legend) &&
+      length(lab_legend) != 4 && length(lab_legend) != 2){
+    stop("Parameter 'lab_legend' should contain two or four names.")
+  }
+  
+  datadim <- dim(data)
+  nrow <- dim(data)['dimy']
+  ncol <- dim(data)['dimx']
+  ncat <- dim(data)['dimcat']
+  
+  # If there is any filenames to store the graphics, process them
+  # to select the right device 
+  if (!is.null(fileout)) {
+    deviceInfo <- s2dverification:::.SelectDevice(fileout = fileout,
+                                                  width = 80 * ncol * figure.width, 
+                                                  height = 80 * nrow,
+                                                  units = size_units, res = res)
+    saveToFile <- deviceInfo$fun
+    fileout <- deviceInfo$files
+  }
+  
+  # Open connection to graphical device
+  if (!is.null(fileout)) {
+    saveToFile(fileout)
+  } else if (names(dev.cur()) == 'null device') {
+    dev.new(units = size_units, res = res,
+            width = 8 * figure.width, height =5)
+  }
+  
+  if (is.null(xlabels)){
+    xlabels=1:ncol
+  }
+  if (is.null(ylabels)){
+    ylabels=1:nrow
+  }
+
+  if (!is.null(brks) && !is.null(cols)){
+    if (length(brks) != length(cols)+1){
+      stop("The length of the parameter 'brks' must be one more than 'cols'.")
+    }
+  }  
+  if (is.null(brks)){
+    brks <- seq(min(data, na.rm=T), max(data, na.rm=T),length.out = 9)
+  }
+  if (is.null(cols)){
+    cols<-rev(brewer.pal(length(brks)-1,'RdBu'))
+  }
+  
+  # The colours for each triangle/category are defined
+  data_cat <- array(cols[length(cols)], dim = datadim)
+  names(dim(data_cat)) <- names(dim(data))
+  for (i in (length(cols) - 1):1) {
+    data_cat[data < brks[i + 1]] <- cols[i]
+  }
+  
+  if(legend){
+    layout(matrix(c(1,2,1,3),2,2,byrow=T),widths =c(10,3.4),heights=c(10,3.5))
+    par(oma=c(1,1,1,1),mar=c(5,4,0,0))
+    if(is.null(lab_legend)){
+      lab_legend=1:ncat
+    }
+  }
+  
+  plot(ncol,nrow,xlim = c(0,ncol),ylim=c(0,nrow), xaxs="i",yaxs='i',type="n", 
+       xaxt="n", yaxt="n",ann=F,axes=F)
+  
+  box(col='black',lwd=1)
+  
+  if (! is.null(toptitle)){
+    title(toptitle, cex=1.5)
+  }
+  
+  if (!is.null(xtitle)){
+    mtext(side = 1, text = xtitle, line = 4, cex=1.5)
+  }
+  if (!is.null(ytitle)){
+    mtext(side = 2, text = ytitle, line = 2.5, cex=1.5)
+  }
+  
+  if (labx){
+    axis(1, at=(1:ncol)-0.5, las=2, labels=xlabels, cex.axis=1.5)
+  }
+  if (laby){
+    axis(2, at=(1:nrow)-0.5, las=2, labels=ylabels, cex.axis=1.5)
+  }
+  
+  
+  #The triangles are plotted
+  for(p in 1:ncol){
+    for(l in 1:nrow){
+      if (ncat==4){
+        coord_triangl <- list(xs=list(c(p-1, p-0.5, p-1),c(p-1, p-0.5, p),c(p, p-0.5, p),c(p-1, p-0.5, p)),
+                              ys=list( c(l-1, -0.5+l, l), c(l-1, -0.5+l, l-1),c(l-1, -0.5+l, l),c(l, -0.5+l, l)))
+        
+        coord_sig <- list(x=c(p-0.75,p-0.5,p-0.25,p-0.5),y=c(l-0.5,l-0.75,l-0.5,l-0.25))
+      }
+      
+      if (ncat==2){
+        coord_triangl <- list(xs=list(c(p-1, p, p-1),c(p-1, p, p)),
+                             ys=list(c(l-1, l, l),c(l-1,l-1, l)))
+        coord_sig <- list(x=c(p-(2/3),p-(1/3)),y=c(l-(1/3),l-(2/3)))
+      }
+      for (n in 1:ncat) {
+        polygon(coord_triangl$xs[[n]],
+                coord_triangl$ys[[n]],
+                col = Subset(
+                  data_cat,
+                  along = c('dimcat', 'dimx', 'dimy'),
+                  indices = list(n, p, l)))
+        if (!is.null(sig_data) &&
+            Subset(sig_data,along = c('dimcat', 'dimx', 'dimy'),
+                   indices = list(n, p, l))) {
+          points(
+            x = coord_sig$x[n],
+            y = coord_sig$y[n],
+            pch = pch_sig,
+            cex = cex_sig,
+            col = col_sig
+          )
+        }
+      }
+    }
+  }
+  
+  # legend
+  
+  if(legend){
+    # Colorbar
+    par(mar=c(0,0,0,0))
+    ColorBar(brks = brks, cols = cols, vert=T,draw_ticks = T, draw_separators = T,
+             #             extra_margin = c(0,0,2.5,0),label_scale = 1.5,...)
+             extra_margin = c(0,0,0,0),label_scale = 1.5,...)
+    
+    par(mar=c(0.5,2.5,0.5,2.5))
+    plot(1,1,xlim = c(0,1),ylim=c(0,1), xaxs="i",yaxs='i',type="n", 
+         xaxt="n", yaxt="n",ann=F,axes=F)
+    
+    box(col=col_leg)
+    p=l=1
+    if (ncat==4){
+      coord_triangl <- list(xs=list(c(p-1, p-0.5, p-1),c(p-1, p-0.5, p),c(p, p-0.5, p),c(p-1, p-0.5, p)),
+                            ys=list( c(l-1, -0.5+l, l), c(l-1, -0.5+l, l-1),c(l-1, -0.5+l, l),c(l, -0.5+l, l)))
+      
+      coord_sig <- list(x=c(p-0.75,p-0.5,p-0.25,p-0.5),y=c(l-0.5,l-0.75,l-0.5,l-0.25))
+    }
+    
+    if (ncat==2){
+      coord_triangl<- list(xs=list(c(p-1, p, p),c(p-1, p, p-1)),
+                           ys=list( c(l-1,l-1, l), c(l-1, l, l)))
+      coord_sig<- list(x=c(p-(2/3),p-(1/3)),y=c(l-(1/3),l-(2/3)))
+    }
+    for (n in 1:ncat) {
+      polygon(coord_triangl$xs[[n]],
+              coord_triangl$ys[[n]],border=col_leg)
+      text(x=coord_sig$x[[n]],y=coord_sig$y[[n]],labels = lab_legend[n],cex=cex_leg,col=col_leg)
+      
+    }
+  }
+  
+  # If the graphic was saved to file, close the connection with the device
+  if (!is.null(fileout)) dev.off()
+}
diff --git a/man/PlotTriangles4Categories.Rd b/man/PlotTriangles4Categories.Rd
new file mode 100644
index 0000000000000000000000000000000000000000..14ab51147cbd08770af4f36bf4df41159492be62
--- /dev/null
+++ b/man/PlotTriangles4Categories.Rd
@@ -0,0 +1,127 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/PlotTriangles4Categories.R
+\name{PlotTriangles4Categories}
+\alias{PlotTriangles4Categories}
+\title{Function to convert any 3-d numerical array to a grid of coloured triangles.}
+\usage{
+PlotTriangles4Categories(
+  data,
+  cols = NULL,
+  brks = NULL,
+  toptitle = NULL,
+  sig_data = NULL,
+  col_sig = "black",
+  pch_sig = 18,
+  cex_sig = 1,
+  labx = TRUE,
+  laby = TRUE,
+  xlabels = NULL,
+  xtitle = NULL,
+  ylabels = NULL,
+  ytitle = NULL,
+  legend = TRUE,
+  lab_legend = NULL,
+  cex_leg = 1,
+  col_leg = "black",
+  fileout = NULL,
+  size_units = "px",
+  res = 100,
+  figure.width = 1,
+  ...
+)
+}
+\arguments{
+\item{data}{array with three named dimensions: 'dimx', 'dimy', 'dimcat', 
+containing the values to be displayed in a coloured image with triangles.}
+
+\item{cols}{A vector of valid colour identifiers for color bar. The length
+must be one less than the parameter 'brks'. Use ColorBar() to generate 
+default values.}
+
+\item{brks}{A vector of the color bar intervals. The length must be one more 
+than the parameter 'cols'. Use ColorBar() to generate default values.}
+
+\item{toptitle}{A string of the title of the grid. Set NULL as default.}
+
+\item{sig_data}{logical array with the same dimensions as 'data' to add layers 
+to the plot. A value of TRUE at a grid cell will draw a dot/symbol on the 
+corresponding triangle of the plot. Set NULL as default.}
+
+\item{col_sig}{colour of the symbol to represent sig_data.}
+
+\item{pch_sig}{symbol to be used to represent sig_data. Takes 18 
+(diamond) by default. See 'pch' in par() for additional 
+accepted options.}
+
+\item{cex_sig}{parameter to increase/reduce the size of the symbols used 
+to represent sig_data.}
+
+\item{xlabels}{A vector of labels of the x-axis The length must be 
+length of the col of parameter 'data'. Set the sequence from 1 to the 
+length of the row of parameter 'data' as default.}
+
+\item{xtitle}{A string of title of the x-axis. Set NULL as default.}
+
+\item{ylabels}{A vector of labels of the y-axis The length must be 
+length of the row of parameter 'data'. Set the sequence from 1 to the 
+length of the row of parameter 'data' as default.}
+
+\item{ytitle}{A string of title of the y-axis. Set NULL as default.}
+
+\item{legend}{A logical value to decide to draw the color bar legend or not. 
+Set TRUE as default.}
+
+\item{lab_legend}{A vector of labels indicating what is represented in each 
+category (i.e. triangle). Set the sequence from 1 to the length of 
+the categories (2 or 4).}
+
+\item{cex_leg}{a number to indicate the increase/reductuion of the lab_legend used 
+to represent sig_data.}
+
+\item{col_leg}{color of the legend (triangles).}
+
+\item{fileout}{A string of full directory path and file name indicating where 
+to save the plot. If not specified (default), a graphics device will pop up.}
+
+\item{size_units}{A string indicating the units of the size of the device 
+(file or window) to plot in. Set 'px' as default. See ?Devices and the 
+creator function of the corresponding device.}
+
+\item{res}{A positive number indicating resolution of the device (file or window) 
+to plot in. See ?Devices and the creator function of the corresponding device.}
+
+\item{...}{The additional parameters to be passed to function ColorBar() in 
+s2dverification for color legend creation.}
+
+\item{xlab}{A logical value (TRUE) indicating if xlabels should be plotted}
+
+\item{ylab}{A logical value (TRUE) indicating if ylabels should be plotted}
+}
+\value{
+A figure in popup window by default, or saved to the specified path.
+}
+\description{
+This function converts a 3-d numerical data array into a coloured 
+grid with triangles. It is useful for a slide or article to present tabular results as 
+colors instead of numbers. This can be used to compare the outputs of two or four categories (
+e.g. modes  of variability, clusters, or forecast systems).
+}
+\examples{
+#Example with random data
+arr1<- arr1<- array(runif(n = 12 * 7 * 4, min=-1, max=1),dim = c(12,7,4))
+names(dim(arr1)) <- c('dimx','dimy','dimcat')
+arr2<- array(TRUE,dim = dim(arr1))
+arr2[which(arr1 < 0.3)] = FALSE
+PlotTriangles4Categories(data = arr1,
+                  cols = c('white','#fef0d9','#fdd49e','#fdbb84','#fc8d59',
+                           '#e34a33','#b30000', '#7f0000'),
+                  brks = c(-1, 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 1), 
+                  lab_legend = c('NAO+', 'BL','AR','NAO-'), 
+                  xtitle = "Target month", ytitle = "Lead time",
+                  xlabels = c("Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul",
+                              "Aug", "Sep", "Oct", "Nov", "Dec"))
+}
+\author{
+History:\cr
+1.0  -  2020-10  (V.Torralba, \email{veronica.torralba@bsc.es})  -  Original code
+}
diff --git a/tests/testthat/test-PlotTriangles4Categories.R b/tests/testthat/test-PlotTriangles4Categories.R
new file mode 100644
index 0000000000000000000000000000000000000000..8105cc91388aba7a1ac20f80041907a5d7a2de0d
--- /dev/null
+++ b/tests/testthat/test-PlotTriangles4Categories.R
@@ -0,0 +1,65 @@
+context("Generic tests")
+test_that("Sanity checks", {
+  expect_error(
+    PlotTriangles4Categories(data = 1:20),
+    paste0("Parameter 'data' must be an array with three dimensions."))
+  
+  data1 <- array(runif(min = -1, max = 1, n = 30), dim=c(5,3,2))
+  expect_error(
+    PlotTriangles4Categories(data = data1),
+    paste0("Parameter 'data' must be an array with named dimensions."))
+  
+  data1 <- runif(min = -1, max = 1, n = 30)
+  dim(data1) <- c(dim1 = 5, dim2 = 2, dim3 = 3)
+  expect_error(
+    PlotTriangles4Categories(data = data1),
+    paste0("Parameter 'data' should contain 'dimx', 'dimy' and 'dimcat' dimension names."))
+  
+  data1 <- runif(min = -1, max = 1, n = 30)
+  dim(data1) <- c(dimx = 5, dimy =2 , dimcat=3)
+  expect_error(
+    PlotTriangles4Categories(data = data1),
+    paste0("Parameter 'data' should contain a dimcat dimension with length equals
+      to two or four as only two or four categories can be plotted"))
+  
+  data1 <- runif(min = -1, max = 1, n = 30)
+  data1[5:10] <- NA
+  dim(data1) <- c(dimx = 5, dimy =3 , dimcat=2)
+  expect_error(
+    PlotTriangles4Categories(data = data1),
+    paste0("Parameter 'data' cannot contain NAs."))
+  
+  data1 <- runif(min = -1, max = 1, n = 30)
+  dim(data1) <- c(dimx = 5, dimy =3 , dimcat=2)
+  expect_error(
+    PlotTriangles4Categories(data = data1,sig_data = 0.5),
+    paste0("Parameter 'sig_data' array must be logical."))
+  
+  expect_error(
+    PlotTriangles4Categories(data = data1, sig_data = TRUE),
+    paste0("Parameter 'sig_data' must be an array with three dimensions."))
+  
+  sig1 <- array(TRUE, dim=c(5,2,3))
+  expect_error(
+    PlotTriangles4Categories(data = data1, sig_data = sig1),
+    paste0("Parameter 'sig_data' must be an array with the same dimensions as 'data'"))
+  
+  sig1 <- array(TRUE, dim= c(5,3,2))
+  dim(sig1) <- c(dimy = 5, dimx =3 , dimcat=2)
+  expect_error(
+    PlotTriangles4Categories(data = data1, sig_data = sig1),
+    paste0("Parameter 'sig_data' must be an array with the same named dimensions as 'data'."))
+  
+  data1 <- runif(min = -1, max = 1, n = 30)
+  dim(data1) <- c(dimx = 5, dimy =3 , dimcat=2)
+  expect_error(
+    PlotTriangles4Categories(data = data1, lab_legend = c('1','2','3')),
+    paste0("Parameter 'lab_legend' should contain two or four names."))
+
+expect_error(
+    PlotTriangles4Categories(data = data1, brks=c(-1,0,1),cols=c('blue','red','black')),
+    paste0("The length of the parameter 'brks' must be one more than 'cols'."))
+
+
+  
+})