Problem with gnuplot in the construction of the histogram - label

Question

everybody:
I'm having problems when it comes to representing the data in the form of a histogram.
I do not know very well how to clearly express what I intend, but my idea is:
3 groups of columns (carbides, borides and nitrides)
in each group of columns, 4 columns (hafnium, zirconium, titanium and
tantalum) each with a grid type.
So far, I have done what appears below, but it does not allow me to continue
My current code is:
reset
fontSpec(s) = sprintf("Times-Roman, %d", s)
set term post eps enhanced fontSpec(16)
set output 'TVsG.eps'
set grid
set auto y
set auto x
ticsFont=fontSpec(16)
set xtics font ticsFont
set ytics font ticsFont
set ylabel "Temperature" font fontSpec(25) offset char -1,0
set xlabel "Group" font fontSpec(25) offset 0,char -1
set style fill pattern border -1
set style data histograms
set boxwidth 1.0
set style histogram clustered gap 1
keyFont=fontSpec(18)
set key spacing 2 font keyFont
set key at graph 0.25, 0.9
fn(v) = sprintf("%.1f", v)
plot \
for [COL=2:4] 'data.txt' using COL:xticlabels(1) title columnheader fs
pattern 2, \
'data.txt' u ($0-1-1./6):2:(fn($2)) w labels font fontSpec(14) offset
char 0,0.5 t '' , \
'data.txt' u ($0-1-1./6):2:(fn($3)) w labels font fontSpec(14) offset
char 0,0.5 t '' , \
'data.txt' u ($0-1+1./6):3:(fn($4)) w labels font fontSpec(14) offset
char 0,0.5 t ''
and my data file
Material Hafnium Zirconium Titanium Tantalum
Carbide 3958 3400 3100 3768
Boride 3380 3245 3225 3040
Nitride 3385 2950 2950 2700
The main problem I have now is the following error:
gnuplot> load 'gnuplot2.txt'
"gnuplot2.txt" line 34: warning: Cannot find or open file "data"
"gnuplot2.txt" line 34: warning: Cannot find or open file "data"
"gnuplot2.txt" line 34: warning: Cannot find or open file "data"
"gnuplot2.txt" line 34: warning: Cannot find or open file "data"
"gnuplot2.txt" line 34: warning: Cannot find or open file "data"
"gnuplot2.txt" line 34: warning: Cannot find or open file "data"
"gnuplot2.txt" line 34: No data in plot
Now I'm at a point, I do not know how to continue

Answer 1

Gnuplot does not find the data file. I see two possible reasons:
The name of the datafile is wrong
The script has something like plot "data.txt", the error message mentions a file "data", note the missing .txt. => Check your script and the actual file name, it might be a simple typo or a missing file extension.
The data file is not in the directory where it is expected.
Add the command pwd (print working directory) as the first command in your script. It will print the directory where it expects the data file. If it is not the correct directory, you can:
move or copy your data file to this directory
use the cd command to change to correct directory
start gnuplot from the correct directory
use the plot command with the file name including path information
You use the load command and gnuplot seems to find the script. So I think most probably the data file should be in the same directory as the script gnuplot2.txt.

Answer 2

So far, this is the image that I have
Indeed, the problem was when selecting the directory in which the data was.
The problem now is that I do not know how I can change the format to give it a different color. Besides, I want to add the compound label on top of each column.
Any suggestions?