Dear colleagues,
I am willing to plot the area average of a rasterstack for several variables
across time.
Let's say I have four variables tempsoi, tempair, gdd and lai. For each of them
I have a rasterstack with their values for 4 time steps.
What I want to do is create a dataframe with:
- the name of the variable
- the year of the measurement
- the average of the correspondent rasterstack layer
So in the same graph I could plot, say, temporal series of lai vs tempair.
With the code below I *almost* get it:
----------------------------------------------------------------------------------------------------------------------------------------------------------------------
library(raster)
library(ggplot2)
# Create random rasterstack and set names
r1 <- r2 <- r3 <- r4 <- raster(nrow = 50, ncol = 100)
r1[] <- 10
r2[] <- 20
r3[] <- 30
r4[] <- 40
s <- stack(r1, r2, r3, r4)
names(s) <- c('X2005.01.01', 'X2006.01.01', 'X2007.01.01', 'X2008.01.01')
# Create random variable names
vars<-c('tempsoi','tempair','gdd','lai')
for( i in 1:length(vars) ) {
v <- vars[i]
# Create empty data.frame
tmp.df1 <- data.frame(g=1, date=rep(NA, length(names(s))), values=NA,
v=NA)
# Loop over years (names), extract raster average values and put in the
data.frame
for ( j in 1:length(names(s)) ) {
tmp.df1$date[j] <- format(as.Date(gsub(pattern='\\.',
replacement='-', substring (names(s)[j],2))))
tmp.df1$values[j] <- mean(getValues(s[[j]]), na.rm = TRUE)
tmp.df1$v <- v
} # end loop over names
# plot data
p <- ggplot(tmp.df1, aes(x=date, y=values, group=g))
print(p + geom_line() + theme_bw() + labs(title = v))
} # end loop vars
----------------------------------------------------------------------------------------------------------------------------------------------------------------------
However, instead of
> tmp.df1
g date values v
1 2005-01-01 10 tempsoi
1 2006-01-01 20 tempsoi
1 2007-01-01 30 tempsoi
1 2008-01-01 40 tempsoi
I would like to have
> tmp.df1
g date values v
1 2005-01-01 10 tempsoi
1 2006-01-01 20 tempsoi
1 2007-01-01 30 tempsoi
1 2008-01-01 40 tempsoi
1 2005-01-01 10 tempair
1 2006-01-01 20 tempair
1 2007-01-01 30 tempair
1 2008-01-01 40 tempair
1 2005-01-01 10 gdd
1 2006-01-01 20 gdd
1 2007-01-01 30 gdd
1 2008-01-01 40 gdd
1 2005-01-01 10 lai
1 2006-01-01 20 lai
1 2007-01-01 30 lai
1 2008-01-01 40 lai
Please help me: how, in this script, can I include the vars in the data.frame
as repetitions?
Thanks in advance,
--
Thiago V. dos Santos
PhD student
Land and Atmospheric Science
University of Minnesota
http://www.laas.umn.edu/CurrentStudents/MeettheStudents/ThiagodosSantos/index.htm
Phone: (612) 323 9898
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