I am making a bar plot using lattice in R where I have data for 4 different years on sources of irrigation for different states. using my code, the bar plot is coming fine but I wish the bar corresponding to the year 1996 to be plotted first followed by the bar corresponding to year 2001 etc. so as to show the increasing area being irrigated by tube-wells. However, I am unable to change the ordering. Here is my data and the R code. Many thanks for your help.
# sample data
irr_atlas <- structure(list(state = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L,
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 3L, 3L, 3L, 3L, 3L, 3L, 3L,
3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 4L, 4L, 4L, 4L, 4L, 4L, 4L,
4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L), .Label = c("ANDHRA PRADESH",
"KARNATAKA", "MADHYA PRADESH", "RAJASTHAN"), class = "factor"),
st_code = c(28L, 28L, 28L, 28L, 28L, 28L, 28L, 28L, 28L,
28L, 28L, 28L, 28L, 28L, 28L, 28L, 29L, 29L, 29L, 29L, 29L,
29L, 29L, 29L, 29L, 29L, 29L, 29L, 29L, 29L, 29L, 29L, 23L,
23L, 23L, 23L, 23L, 23L, 23L, 23L, 23L, 23L, 23L, 23L, 23L,
23L, 23L, 23L, 8L, 8L, 8L, 8L, 8L, 8L, 8L, 8L, 8L, 8L, 8L,
8L, 8L, 8L, 8L, 8L), year = c(1996L, 1996L, 1996L, 1996L,
2001L, 2001L, 2001L, 2001L, 2006L, 2006L, 2006L, 2006L, 2011L,
2011L, 2011L, 2011L, 1996L, 1996L, 1996L, 1996L, 2001L, 2001L,
2001L, 2001L, 2006L, 2006L, 2006L, 2006L, 2011L, 2011L, 2011L,
2011L, 1996L, 1996L, 1996L, 1996L, 2001L, 2001L, 2001L, 2001L,
2006L, 2006L, 2006L, 2006L, 2011L, 2011L, 2011L, 2011L, 1996L,
1996L, 1996L, 1996L, 2001L, 2001L, 2001L, 2001L, 2006L, 2006L,
2006L, 2006L, 2011L, 2011L, 2011L, 2011L), irr_area = c(1.84066,
0.942819, 0.82886, 0.853502, 1.54922, 0.825659, 0.542492,
1.53412, 1.72969, 0.70271, 0.637221, 1.53894, 1.99893, 0.678425,
0.819829, 1.70708, 0.921594, 0.231669, 0.316999, 0.358529,
0.91339, 0.207157, 0.426549, 0.481061, 0.921255, 0.18192,
0.426145, 0.547193, 0.930802, 0.148065, 0.377149, 1.51843,
1.59425, 0.112145, 2.67683, 0.540054, 1.48056, 0.030502,
1.63696, 0.563948, 1.12595, 0.058667, 2.46494, 1.15004, 1.10444,
0.157069, 2.64378, 2.14177, 1.55814, 0.106623, 2.71347, 0.644683,
1.35746, 0.030586, 2.41845, 0.935234, 1.76933, 0.054374,
2.46197, 1.76918, 1.62587, 0.050299, 2.14737, 2.82708),irr_source = structure(c(1L,2L, 4L, 3L, 1L, 2L, 4L, 3L, 1L, 2L, 4L, 3L, 1L, 2L, 4L, 3L,
1L, 2L, 4L, 3L, 1L, 2L, 4L, 3L, 1L, 2L, 4L, 3L, 1L, 2L, 4L,
3L, 1L, 2L, 4L, 3L, 1L, 2L, 4L, 3L, 1L, 2L, 4L, 3L, 1L, 2L,
4L, 3L, 1L, 2L, 4L, 3L, 1L, 2L, 4L, 3L, 1L, 2L, 4L, 3L, 1L,
2L, 4L, 3L), .Label = c("Canal", "Tank", "Tube", "Well"), class = "factor")), .Names = c("state","st_code", "year", "irr_area", "irr_source"), class = "data.frame", row.names = c(NA, -64L))
Code for plot...
library(lattice)
barchart(~irr_area | factor(state) + factor(irr_source),
group=year, data=irr_atlas, auto.key=list(space="right"))
As mentioned, ordering of groups in R graphics is usually determined by the ordering of the factor variable. So, you can reorder your factors with factor and its levels argument.
library(lattice)
barchart(~irr_area | factor(state) + factor(irr_source),
group=factor(year, levels=sort(unique(year), decreasing=T)), # change the order of years
data=irr_atlas, auto.key=list(space="right"))
You can switch it back the other way by changing decreasing=F.