# R code to plot latitudinal profiles of mean slope, along with both

# RMSE and correlation coefficients comparing fused layers with both the

# raw ASTER and with the Canada DEM

#

# Jim Regetz

# NCEAS

# Created on 08-Jun-2011

library(raster)

datadir <- "/home/regetz/media/temp/terrain/slope"

# load slope rasters

s.aster <- raster(file.path(datadir, "aster_300straddle_s.tif"))

s.srtm <- raster(file.path(datadir, "srtm_150below_s.tif"))

s.uncor <- raster(file.path(datadir, "fused_300straddle_s.tif"))

s.can <- raster(file.path(datadir, "cdem_300straddle_s.tif"))

# extract raster latitudes for later

lats300 <- yFromRow(s.aster, 1:nrow(s.aster))

lats150 <- yFromRow(s.srtm, 1:nrow(s.srtm))

# initialize output pdf device driver

pdf("slope-assessment.pdf", height=8, width=11.5)

#

# plot latitudinal profiles of mean slope

#

par(mfrow=c(2,2), omi=c(1,1,1,1))

lines(lats300, rowMeans(as.matrix(s.aster), na.rm=TRUE), col="blue")

lines(lats150, rowMeans(as.matrix(s.srtm), na.rm=TRUE), col="red")

legend("topright", legend=c("ASTER", "SRTM", "CDED"), col=c("blue",

    "red", "black"), lty=c(1, 1), bty="n")

mtext(expression(paste("Latitudinal profiles of mean slope (",

    136*degree, "W to ", 96*degree, "W)")), adj=0, line=2, font=2)

plot(lats300, rowMeans(as.matrix(s.bg), na.rm=TRUE), type="l",

    xlab="Latitude", ylab="Mean slope", ylim=ylim)

text(min(lats300), max(ylim)-0.5, pos=4, font=3, labels="gaussian blend")

abline(v=60, col="red", lty=2)

#

# plot latitudinal profiles of RMSE

#

# simple helper function to calculate row-wise RMSEs

    diffs <- abs(as.matrix(r1) - as.matrix(r2))

    if (!missing(use)) diffs[!use] <- NA

    sqrt(rowMeans(diffs^2, na.rm=na.rm))

par(mfrow=c(2,3), omi=c(1,1,1,1))

# ...with respect to ASTER

plot(lats300, rmse(s.uncor, s.aster), type="l", xlab="Latitude",

    ylab="RMSE", ylim=c(0, 5))

lines(lats150, rmse(crop(s.uncor, extent(s.srtm)), s.srtm), col="blue")

legend("topright", legend=c("ASTER", "SRTM"), col=c("black", "blue"),

    lty=c(1, 1), bty="n")

mtext(expression(paste(

    "Slope discrepancies with respect to separate ASTER/SRTM components (",

    136*degree, "W to ", 96*degree, "W)")), adj=0, line=2, font=2)

    lty=c(1, 1), bty="n")

plot(lats300, rmse(s.bg, s.aster), type="l", xlab="Latitude",

    ylab="RMSE", ylim=c(0, 5))

lines(lats150, rmse(crop(s.bg, extent(s.srtm)), s.srtm), col="blue")

legend("topright", legend=c("ASTER", "SRTM"), col=c("black", "blue"),

    lty=c(1, 1), bty="n")

text(min(lats300), 4.5, pos=4, font=3, labels="gaussian blend")

abline(v=60, col="red", lty=2)

# ...with respect to CDEM

plot(lats300, rmse(s.uncor, s.can), type="l", xlab="Latitude",

    ylab="RMSE", ylim=c(0, 5))

mtext(expression(paste(

    "Slope discrepancies with respect to Canada DEM (",

    136*degree, "W to ", 96*degree, "W)")), adj=0, line=2, font=2)

plot(lats300, rmse(s.bg, s.can), type="l", xlab="Latitude",

    ylab="RMSE", ylim=c(0, 5))

text(min(lats300), 4.5, pos=4, font=3, labels="gaussian blend")

abline(v=60, col="red", lty=2)

#

# plot latitudinal profiles of correlation coefficients

#

# simple helper function to calculate row-wise correlation coefficients

corByLat <- function(r1, r2, rows) {

    if (missing(rows)) {

        rows <- 1:nrow(r1)

    }

    m1 <- as.matrix(r1)

    m2 <- as.matrix(r2)

    sapply(rows, function(row) cor(m1[row,], m2[row,],

        use="pairwise.complete.obs"))

}

par(mfrow=c(2,3), omi=c(1,1,1,1))

ylim <- c(0.65, 1)

# ...with respect to ASTER

plot(lats300, corByLat(s.uncor, s.aster), type="l", xlab="Latitude",

    ylab="Correlation", ylim=ylim)

lines(lats150, corByLat(crop(s.uncor, extent(s.srtm)), s.srtm), col="blue")

legend("bottomright", legend=c("ASTER", "SRTM"), col=c("black", "blue"),

    lty=c(1, 1), bty="n")

mtext(expression(paste(

    "Slope correlations with respect to separate ASTER/SRTM components (",

    136*degree, "W to ", 96*degree, "W)")), adj=0, line=2, font=2)

    lty=c(1, 1), bty="n")

plot(lats300, corByLat(s.bg, s.aster), type="l", xlab="Latitude",

    ylab="Correlation", ylim=ylim)

lines(lats150, corByLat(crop(s.bg, extent(s.srtm)), s.srtm), col="blue")

legend("bottomright", legend=c("ASTER", "SRTM"), col=c("black", "blue"),

    lty=c(1, 1), bty="n")

text(min(lats300), min(ylim), pos=4, font=3, labels="gaussian blend")

abline(v=60, col="red", lty=2)

# ...with respect to CDEM

plot(lats300, corByLat(s.uncor, s.can), type="l", xlab="Latitude",

    ylab="Correlation", ylim=ylim)

mtext(expression(paste(

    "Slope correlations with respect to Canada DEM (",

    136*degree, "W to ", 96*degree, "W)")), adj=0, line=2, font=2)

plot(lats300, corByLat(s.bg, s.can), type="l", xlab="Latitude",

    ylab="Correlation", ylim=ylim)

text(min(lats300), min(ylim), pos=4, font=3, labels="gaussian blend")

abline(v=60, col="red", lty=2)

# close pdf device driver

dev.off()