Redrawing Excel figures on gnuplot - gnuplot

Question

I was working on excel and drew two histograms shown below, I have been told to redraw them using gnuplot on windows which is very new to me.
The original graph that I want to redraw is this.
Area 1 Area 2
Case 1 Case 2 Case 1 Case 2
Parameter 1 36 66 31 72
Parameter 2 57 91 44 85
Parameter 3 62 90 50 85
My file is a text file and I wrote the above table as follows as I am not sure how to group the different columns together.
Area Area1 Area1 Area2 Area2
Case Case1 Case2 Case1 Case2
Parameter_1 36 66 31 72
Parameter_2 57 91 44 85
Parameter_3 62 90 50 85
I used the following commands and got a histogram that is grouped in the wrong way.
clear
reset
unset key
set style data histogram
set style fill solid border
set style histogram clustered
plot for [COL=2:5] 'date_mins.tsv' using COL:xticlabels(1) title columnheader
Kindly guide me on how to group columns together and also how to add the numbers on top of the bars. {The graph should be same as the one excel generated one.}

Answer 1

To be honest I'm regularly puzzled with histograms in gnuplot, apparently I'm not the only one. In gnuplot console, check help histograms.
Although, there are a few histogram examples on the gnuplot homepage, but of course not all possible variations can be covered.
Apparently, this plotting style is a bit confusing to understand.
This would maybe explain that there are more than 800 questions on SO on histograms with gnuplot.
I'm not sure if or how you can get your desired histogram efficiently, maybe there is an easy way.
I would do it "manually" with the plotting style with boxes.
Check the example below as a starting point. There are a few strange workarounds included, e.g. getting the titles into an array in an earlier plot for later use.
Code:
### special histogram
reset session
$Data <<EOD
Area Area1 Area1 Area2 Area2
Case Case1 Case2 Case1 Case2
"Parameter 1" 36 66 31 72
"Parameter 2" 57 91 44 85
"Parameter 3" 62 90 50 85
EOD
set style fill solid noborder
set boxwidth 0.8
set key noautotitle out center bottom horizontal reverse Left samplen 1 width 2
A=2 # Areas
C=2 # Cases
P=3 # Parameters
g=1 # gap
PosX(a,c,p) = ((a-1)*C*(P+g)) + (c-1)*(P+g) + p
PosY(a,c) = column((a-1)*C+c+1)
PosXArea(a) = (PosX(a,C,P)+PosX(a-1,C,P))*0.5
PosXCase(a,c) = (PosX(a,c,P)+PosX(a,c-1,P))*0.5
myColor(p) = int(word("0x5b9bd5 0xed7d31 0xa5a5a5",int(p)))
myValue(a,c) = strcol((a-1)*C+c+1)
set grid y
set xlabel "\n\n\n" # get empty space below the plot
set format x "" # no xtic labels
set yrange[0:]
array Titles[P] # array for titles
plot for [a=1:A] for [c=1:C] $Data u (PosX(a,c,$0)):(PosY(a,c)):(myColor($0+1)) skip 2 w boxes lc rgb var , \
for [a=1:A] for [c=1:C] '' u (PosX(a,c,$0)):(PosY(a,c)):(Titles[int($0+1)]=strcol(1), myValue(a,c)) skip 2 w labels offset 0,0.7, \
for [a=1:A] for [c=1:C] '' u (PosXCase(a,c)):(0):(myValue(a,c)) every ::1::1 w labels offset 0,-1, \
for [a=1:A] '' u (PosXArea(a)):(0):('\n\n'.myValue(a,1)) every ::0::0 w labels offset 0,-1, \
for [p=1:P] keyentry w boxes lc rgb myColor(p) ti Titles[p]
### end of code
Result: