在R或gnuplot中以相似的比例绘制不同的等高线图

Question

I am new to R for plotting, and I wish to do contour plots for several files. and here is what I have got so far. My file has 3 columns, X,Y,Z, and with some nan values. Since lattice does not allow Inf/NaN values, I had to remove them prior, and do some interpolation.

data <- read.table("file", sep=",", header=T)
mydata <- na.omit(data)
library(akima)
library(lattice)
s = interp(mydata$X, mydata$Y, mydata$Z)
filled.contour(s, xlim= c(5,25), ylim=c(40,180))

This does gives some results, but there are things I am not able to do:

1. To get contour lines on the graph.
2. Also there are like 3 files with different z ranges, say one from (0-18), (0-20), (0-25). I wish to adjust and rescale them to provide similar color scale on graph, for instance, the '15' value should be similar color on all three.

I am more familiar with gnuplot, but there also the problem is with the ranges, as the range always autoscale to color, and it seems difficult to control the range. Any help with that is also deeply appreciated.
I may be doing something wrong, so in case anybody could help me out, and provide to right direction, or right software, I will be grateful.

Answer 1

There are demos here for how to make contours in gnuplot. Are you having trouble in the sense that you have code to make a contour plot but it does not work?

To answer your second question, in gnuplot the command you probably want is

set cbrange [CB_MIN:CB_MAX]

This sets the range of values which will be colored according to the current palette. You would just have to issue the same set cbrange command for all three plots you are making. If you want to automatically set the cbrange to the min/max on all files, you can use the stats command (in version 4.6 or newer, otherwise it is more tricky):

stats 'datafile1' using 3 name 'd1'
stats 'datafile2' using 3 name 'd2'
stats 'datafile3' using 3 name 'd3'
datamin_z = (d1_min<d2_min&&d1_min<d3_min?d1_min:d2_min<d3_min?d2_min:d3_min)
datamax_z = (d1_max>d2_max&&d1_max>d3_max?d1_max:d2_max>d3_max?d2_max:d3_max)
set cbrange [datamin_z:datamax_z]