Range change based on continuous (fuzzy) values

This function, included in the fuzzySim package (version 1.6 just released), uses the fuzzyOverlay function in the previous post and then quantifies overall range change (including gain, loss, maintenance/stability and total change) based on the continuous predictions of two species distribution models (see Gutiérrez-Rodríguez et al., in press).

fuzzyRangeChange <- function(pred1, pred2, number = TRUE, prop = TRUE, na.rm = TRUE, round.digits = 2, measures = c("Gain", "Loss", "Stable_presence", "Stable_absence", "Balance"), plot = TRUE, col = colorRampPalette(c("white", "black"))(length(measures)), ...) {
 
  # version 1.4 (23 Mar 2016)
 
  stopifnot(ncol(pred1) == ncol(pred2),
            all(pred1[is.finite(pred1)] >= 0 && pred1[is.finite(pred1)] <= 1),
            all(pred2[is.finite(pred2)] >= 0 && pred2[is.finite(pred2)] <= 1)
  )
 
  if (!number & !prop) stop ("Nothing to calculate if both 'number' and 'prop' are FALSE.")
 
  values <- vector("numeric", length(measures))
  names(values) <- measures
  if ("Gain" %in% measures)  values["Gain"] <- sum(fuzzyOverlay(data.frame(pred1, pred2), op = "expansion", na.rm = na.rm), na.rm = na.rm)
  if ("Loss" %in% measures)  values["Loss"] <- sum(fuzzyOverlay(data.frame(pred1, pred2), op = "contraction", na.rm = na.rm), na.rm = na.rm)
  if ("Stable_presence" %in% measures)  values["Stable_presence"] <- sum(fuzzyOverlay(data.frame(pred1, pred2), op = "maintenance", na.rm = na.rm), na.rm = na.rm)
  if ("Stable_absence" %in% measures)  values["Stable_absence"] <- sum(fuzzyOverlay(1 - data.frame(pred1, pred2), op = "maintenance", na.rm = na.rm), na.rm = na.rm)
  if ("Balance" %in% measures)  values["Balance"] <- sum(fuzzyOverlay(data.frame(pred1, pred2), op = "change", na.rm = na.rm), na.rm = na.rm)
 
  result <- data.frame(Measure = measures, Number = values)
 
  if (prop) {
    if (na.rm) n <- length(na.omit(pred1))
    else n <- length(pred1)
    range.size <- sum(pred1, na.rm = na.rm)
    stable.abs <- result[result$Measure == "Stable_absence", "Number"]
    result$Proportion <- result[ , "Number"] / range.size
    result[result$Measure == "Stable_absence", "Proportion"] <- stable.abs / (n - range.size)
  }
 
  if (!number) {
    result <- result[ , - (ncol(result) - 1)]
  }
 
  if (plot) {
    barplot(result[ , ncol(result)], legend.text = rownames(result), col = col, ...)
    abline(h = 0)
  }
 
  result[ , "Measure"] <- NULL
  if (is.finite(round.digits))  result <- round(result, round.digits)
 
  result
}

[presented with Pretty R]

The function will produce numeric and (since FuzzySim 1.7.2) also graphical results quantifying the fuzzy overall changes:

FuzzyRangeChange

You can install and load fuzzySim (>= 1.6) and then check help(fuzzyRangeChange) for further  info and reproducible usage examples.

 

REFERENCES

Gutiérrez-Rodríguez J., Barbosa A.M. & Martínez-Solano I. (in press) Present and past climatic effects on the current distribution and genetic diversity of the Iberian spadefoot toad (Pelobates cultripes): an integrative approach. Journal of Biogeography.

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Plot column(s) of a polygon vector map

NOTE: I recently had a tutorial on the cartography R package, which makes mapping columns of a data frame much less troublesome. You may want to look at that instead.

If you have a polygon vector map in R and want to quickly map the values in one or more columns of its attribute table, you can use the plotMapColumns function. There’s an option to rasterize the map before plotting, which may be considerably faster and is TRUE by default, but you’ll need to use an appropriate raster.upscale value. This is the number by which the range of coordinates should be divided to get the number of pixels for the maps to be plotted; it’s advised to first check your range(coordinates(map)) and see for yourself which raster.upscale divisor will make reasonably computable raster maps – e.g., for geographical lat-lon, an upscale factor of 1 will usually work (you’ll have at most 360 x 180 pixels; actually you may want to lower raster.upscale to 0.5 or 0.3 if you need more detailed maps); but for a UTM projection (whose coordinates can be much larger values) you may need an upscale.factor of 10000 to get a reasonably computable number of pixels.

plotMapColumns <- function(map, # SpatialPolygons object
                           columns, # index(es) of column(s) of map@data containing the values to plot (there will be one output map per column)
                           rasterize = TRUE, # number by which the difference between maximum and minimum coordinates should be divided to get the number of pixels (if rasterize = TRUE); it's advised to first calculate min and max coordinates and see for yourself which divisor will make reasonably computable raster maps (e.g., for geographical lat-lon an upscale factor of 1 may work, but for a UTM projection you may need an upscale of factor 10,000!)
                           raster.upscale = 1, 
                           ...) # additional arguments for (sp)plot function
  {

  stopifnot(raster.upscale > 0 | is.null(raster.upscale),
            require(raster) | rasterize == FALSE
            )
 
  if (!all(columns %in% 1:length(names(map)))) stop ("index out of bounds; 'columns' must exist in map@data.")
 
  if (rasterize) {
    xmin <- min(coordinates(map)[,1])
    xmax <- max(coordinates(map)[,1])
    ymin <- min(coordinates(map)[,2])
    ymax <- max(coordinates(map)[,2])
    wdth <- round(xmax - xmin)
    hght <- round(ymax - ymin)
 
    #if (raster.upscale == "auto") {
      #max.length <- max(wdth, hght)
      #if (max.length > 500) raster.upscale <-
    #}
 
    #if (!is.null(max.rast.dim)) {
    #  rast.dim <- wdth * hght
    #}
 
    wdth <- wdth / raster.upscale
    hght <- hght / raster.upscale
    message("plotting map(s) with ", wdth, "x", hght, " pixels; consider rising 'raster.upscale' if this is taking too long, or lowering it if the resulting maps are too coarse.")
    require(raster)
    rast <- raster(nrows = hght, ncols = wdth, xmn = xmin, xmx = xmax, ymn = ymin, ymx = ymax)
  }  # end if rasterize I
 
  #if (centroids) {
  #  attr.table <- map@data
  #  map <- SpatialPointsDataFrame(coordinates(map))
  #  map@data <- attr.table
  #  rast <- raster(map)
  #} else {
    require(sp)
  #}
 
  n.cols <- length(columns)
  col.count <- 0
  for (i in columns) {
    col.count <- col.count + 1
    message("Plotting column ", col.count, " of ", n.cols, "...")
    if (rasterize) {
      map.rast <- rasterize(x = map, y = rast, field = names(map)[i], fun = 'last')
      plot(map.rast, main = names(map)[i], ...)
    }  # end if rasterize II
    else {
      print(spplot(map, zcol = names(map)[i], main = names(map)[i], ...))
    }  # end else
  }  # end for i
  message("Finished!")
}

[presented with Pretty R]

Usage example:

# download, unzip and import a map of countries:
download.file("http://biogeo.ucdavis.edu/data/world/countries_shp.zip", destfile = "countries_shp.zip")
unzip("countries_shp.zip")
countries <- rgdal::readOGR(dsn = ".", layer= "countries")
 
# see the data in the attributes table:
head(countries)
names(countries)
 
# use plotMapColumns with and without rasterizing:
plotMapColumns(countries, columns = 17:18, rasterize = TRUE, raster.upscale = 1)
plotMapColumns(countries, columns = 18, rasterize = FALSE)  # slower

You can add arguments for the (sp)plot function, to get e.g. different colour schemes. The plotMapColumns function is not (yet) included in a package.

Calculate zonal statistics from rasters in multiple zip files

This is a wrapper for the zonalFromZip function published in the previous post, for when you have multiple zip files with multiple raster files each (as in the WorldClim paleo-climate database), and you want to extract zonal statistics for them all automatically. To use it, you’ll need to have the zonalFromZip function loaded, as well as the raster R package.

zonalsFromZips <- function(zip.files, zones.rast, rast.file.ext = ".tif", aux.file.ext = NULL, verbosity = 1, ...) {
  results <- vector("list", length(zip.files))
  names(results) <- basename(tools::file_path_sans_ext(zip.files))
  for (f in 1:length(zip.files)) {
    message("\nUNZIPPING FILE ", f, " OF ", length(zip.files), " (", basename(zip.files[f]), ")...")
    results[[f]] <- zonalFromZip(zip.file = zip.files[f], zones.rast = zones.rast, rast.file.ext = rast.file.ext, aux.file.ext = aux.file.ext, verbosity = verbosity, ...)
  }; rm(f)
  message("\nFINISHED ALL!")
  return(results)
}  # end zonalsFromZips function

 

The result is a list of dataframes, each containing the zonal stats for one of the .zip files of rasters. Usage example:

LGM.zonals <- zonalsFromZips(zip.files = list.files("/home/joe/LGM", full.names = TRUE), zones.rast = utm10.raster)

[presented with Pretty R]

 

Calculate zonal statistics from rasters in a zip file

Imagine you have a zipped folder with a bunch of raster maps containing variables (e.g. the ones you can download from WorldClim or from CliMond), and you need to calculate zonal statistics from each of these rasters. The zonaFromZip function, provided below, automates this process without the need to unzip the folders. It extracts one raster at a time from the .zip, imports it to R, calculates zonal statistics for your zones raster map (the ‘mean’ function is used by default, but you can provide any other argument accepted by the zonal function of the R raster package), and then deletes the unzipped file before unzipping the next one, therefore requiring minimal disk space.

zonalFromZip <- function (zip.file, zones.rast, rast.file.ext = ".tif", aux.file.ext = NULL, delete.unzipped = TRUE, verbosity = 2, ...)
  # zip.file: path to the zip containing the raster maps to calculate zonal stats from
  # zones.rast: raster map (in your R workspace) containing the spatial units to calculate zonal stats to
  # rast.file.ext: file extension for the raster maps on disk
  # aux.file.ext: file extension for the auxiliary files (e.g. ".hdr" for .bil raster files, or ".rdc" for Idrisi .rst files)
  # ...: arguments to pass to the 'zonal' function from the 'raster' package
{
  require(raster)
  rast.files <- unzip(zip.file, list = TRUE) $ Name
  var.names <- unique(tools::file_path_sans_ext(rast.files))
  n.var <- length(var.names)
  zonal.stats <- vector("list", length(var.names))
  names(zonal.stats) <- var.names
  for (i in 1:n.var) {
    if (verbosity >= 1) message("Getting variable ", i, " of ", n.var)
    if (verbosity >= 2) message("  - unzipping file...")
    unzip(zip.file, files = paste0(var.names[i], rast.file.ext))
    if (!is.null(aux.file.ext)) unzip(zip.file, files = paste0(var.names[i], aux.file.ext))
    var.rast <- raster(paste0(var.names[i], rast.file.ext))
    if (!compareRaster(var.rast, zones.rast, stopiffalse = FALSE)) {
      if (verbosity >= 2) message("  - cropping to zones raster...")
      var.rast <- crop(var.rast, zones.rast)
    }
    if (verbosity >= 2) message("  - calculating zonal stats...")
    zonal.stats[[i]] <- raster::zonal(var.rast, zones.rast, ...)
    if (verbosity >= 2) message("  - deleting unzipped file...")
    if (delete.unzipped) {
      unlink(list.files()[grep(pattern = paste0(var.names[i], rast.file.ext), x = list.files())])
      if (!is.null(aux.file.ext)) unlink(list.files()[grep(pattern = paste0(var.names[i], aux.file.ext), x = list.files())])
    }
  }
  if (verbosity >= 1) message("Converting results to data frame...")
  zonal.stats <- as.data.frame(zonal.stats)
  zonal.stats <- subset(zonal.stats, select = c(1, seq(2, ncol(zonal.stats), 2)))
  colnames(zonal.stats)[1] <- "zone"
  colnames(zonal.stats)[-1] <- var.names
  if (verbosity >= 1) message("Finished!")
  return(zonal.stats)
}

 

Mind that you need the raster R package installed for this, and a raster map of the spatial units (zones) to which you want to extract the raster variables.Usage examples:

LGM.CCSM4.utm10 <- zonalFromZip(zip.file = "LGM/CCSM4.zip", zones.rast = utm10.rst, rast.file.ext = ".tif", aux.file.ext = NULL)
head(LGM.CCSM4.utm10)
 
WClim.utm10 <- zonalFromZip(zip.file = "bio_2-5m_bil.zip", zones.rast = utm10.rst, rast.file.ext = ".bil", aux.file.ext = ".hdr")
head(WClim.utm10)

Example for several .zip files within a folder at once (DEPRECATED – see next post’s zonalsFromZips function instead):

for (f in list.files("LGM")) {  # "LGM" is the folder containing the zip files to extract zonal stats from
  name <- paste("LGM", tools::file_path_sans_ext(f), "utm10", sep = ".")
  zonstat <- zonalFromZip(zip.file = paste("LGM", f, sep = "/"), zones.rast = u10.rst, raster.ext = ".tif", fun = "mean")
  assign(name, zonstat)
}

[presented with Pretty R]

 

Convert geographical coordinates from degree-minute-second to decimal degrees

essIf you have latitude and/or longitude data in sexagesimal degrees, in the form degreesº minutes’ seconds” hemisfere (e.g. 41° 34′ 10.956″ N  or  8° 37′ 47.1036″ W, with or without spaces in between), the dms2dec function can convert them to decimal degrees, which are usually required for mapping. This function is not included in a package, but it’s in the “Supplementary Info” of Zanolla et al. (in review), so please cite this paper if you use the function.

dms2dec <- function(dms, separators = c("º", "°", "\'", "\"")) {
  # version 1.0 (25 Sep 3013)
  # dms: a vector (or column) of latitude or longitude in degrees-minutes-seconds-hemisfere, e.g. 41° 34' 10.956" N (with or without spaces)
  # separators: the characters that are separating degrees, minutes and seconds in dms

  dms <- as.character(dms)
  dms <- gsub(pattern = " ", replacement = "", x = dms)
  for (s in separators) dms <- gsub(pattern = s, replacement = "_splitHere_", x = dms)

  splits <- strsplit(dms, split = "_splitHere_")
  n <- length(dms)
  deg <- min <- sec <- hem <- vector("character", n)

  for (i in 1:n) {
    deg[i] <- splits[[i]][1]
    min[i] <- splits[[i]][2]
    sec[i] <- splits[[i]][3]
    hem[i] <- splits[[i]][4]
  }

  dec <- as.numeric(deg) + (as.numeric(min) / 60) + (as.numeric(sec) / 3600)
  sign <- ifelse (hem %in% c("N", "E"), 1, -1)
  dec <- sign * dec
  return(dec)
}  # end dms2dec function 

[presented with Pretty R]

Usage example, from a table called mydata:

LatLonTable

mydata$latitude.decimal <- dms2dec(mydata$Latitude)

mydata$longitude.decimal <- dms2dec(mydata$Longitude)

 

REFERENCES:

Zanolla M., Altamirano M., Carmona R., De La Rosa J., Souza-Egipsy V., Sherwood A., Tsiamis K., Barbosa A.M., Muñoz A.R. & Andreakis N. (in press) Assessing global range expansion in a cryptic species complex: insights from the red seaweed genus Asparagopsis (Florideophyceae). Journal of Phycology, accepted.

Upscale UTM 10 x 10 km cells to 20, 50 or 100 km

If you have a map with/or a data table of UTM 10 x 10 km cells with the corresponding UTM codes, and want to upscale them to 20 x 20, 50 x 50 or 100 x 100 km cells, you can use the UTM10upscale function to create cell codes that group the UTM codes accordingly. This function is not included in an R package, but it is being included in the QGIS Processing toolbox.

UTM10upscale <- function(UTMcode, size) {
  # version 1.3 (14 Mai 2013)
  # UTMcode: a vector string of UTM 10x10 km codes (e.g. MC58 or 29SMC58)
  # size: the size (in square km) of the UTM cells for which to create codes; must be 20, 50 or 100
  if (missing(size)) stop ("Argument 'size' is missing, with no default.")
  if (!(size %in% c(20, 50, 100))) stop ("'size' must be a multiple of 10 and a divisor of 100 - i.e. 20, 50 or 100.")
  UTMcode <- as.character(UTMcode)
  nc <- unique(nchar(UTMcode))
  if (length(nc) != 1) stop ("All elements of UTMcode must have the same number of characters.")
  utm10letters <- substr(UTMcode, nc - 4, nc -2)
  if(size == 100)  upscaled.code <- utm10letters
  else {
    utm10x <- substr(UTMcode, nc - 1, nc - 1)  # penultimate digit of UTMcode
    utm10y <- substr(UTMcode, nc, nc)  # last digit of UTMcode
    utm10index <- 0 : 9
    if (size == 20)  upscaled.index <- rep(letters[1 : 5], each = 2)
    else if (size == 50) upscaled.index <- rep(LETTERS[1 : 2], each = 5)
    n <- length(UTMcode)
    upscaled.x <- upscaled.y <- vector("integer", n)
    for (i in 1 : n) {
      x <- which(utm10index == utm10x[i])
      y <- which(utm10index == utm10y[i])
      upscaled.x[i] <- upscaled.index[x]
      upscaled.y[i] <- upscaled.index[y]
    }  # end for i
    upscaled.code <- paste(utm10letters, upscaled.x, upscaled.y, sep = "")
    }  # end if size 100 else
  return(upscaled.code)
}  # end UTM10upscale function

[presented with Pretty R]

Note that the resulting codes for 20×20 and for 50×50 km cells (namely the last two characters) are not “official” UTM codes, just ones that I made up. I used letters instead of numbers, with lower case for 20-km and upper case for 50-km cells, so that these codes cannot be confused with the UTM 10×10 km codes.

Then you just have to add a column with the new codes to your map’s table of attributes, and use e.g. a spatial R package or a GIS to dissolve the UTM 10 x 10 km cells using the values in this column. You can also use R’s aggregate function to summarize your data into the upscaled cells.

mydata$utm20 <- utm10upscale(mydata$utm10, size = 20)
mydata$utm50 <- utm10upscale(mydata$utm10, size = 50)