Create functions in gnuplot

Question

I am reading data from a file, and I determine the min and the max.

I would like to implement a function where if min==max, then min = 0

I have thios so far:

reset

# Define two helper functions
ismin(x) = (x<min)?min=x:0
ismax(x) = (x>max)?max=x:0

# Initialise the 'global' vars
max=-1e38
min=1e38

plot "Data.txt" u 0:(ismin($3)*ismax($3))

#set terminal windows
set terminal png medium size 900,600
set output "Data.png"

print min
print max

iseq(min,max) = (min == max)?min = 0 :0

print min
print max

How can I set min to 0 if min==max?

Thank you

andyras · Accepted Answer · 2013-02-21 14:40:04Z

1

How about an if statement:

if (min == max) min = 0

answered Feb 21, 2013 at 14:40

andyras

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Comments

theozh · Accepted Answer · 2025-11-05 19:29:09Z

It depends on what you want to do... since gnuplot 4.6.0 (March 2012) you have STATS (check help stats). Assuming you have the following data in SO15004547.dat:

Test A:

or alternatively Test B:

So, I see at least two ways:

Script:

### find min, max and set min=0 if min==max
reset session

FILE = "SO15004547.dat"

# version 1 using STATS
stats FILE u 1 nooutput
max = STATS_max
min = STATS_min == STATS_max ? 0 : STATS_min
print min, max

# version 2 using plot
min = max = NaN
getmin(x) = x>min ? min : x
getmax(x) = x<max ? max : x
plot FILE u 0:(min=getmin($1),max=getmax($1), $1)
min = min==max ? 0 : min
print min, max

### end of script

Result:

Test A:

-99.0, 55.0
-99.0, 55.0

Test B:

0, 33.0
0, 33.0

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