Re: [Gnuplot-info] how to draw Gaussian shape with histogram

[Thomas S. <t.s...@fz...>]

your data look like an energy loss spectrum of a particle detector.

in order to fit a gaussian you first need to do a background
subtraction. we assume an exponential function here.

background(x)=b0*exp(-x/bc)

we use only the two points at x=100 and x=700, resp. to determine
the background.

fit background(x) 'ts.dat' using ($1==100||$1==700?$1:0/0):2 via b0, b

and then we fit the gaussian

fit [90:800] gauss(x) 'ts.dat' using 1:($2-background($1)) via position,
amplitude, sigma

the complete script:

datafile = 'ts.dat'
set samples 1000
set yrange [0:*]
gauss(x)=amplitude/(sigma*sqrt(2.*pi))*exp(-(x-position)**2/(2.*sigma**2))
background(x)=b0*exp(-x/bc)
b0=30
bc=200
fit background(x) datafile using ($1==100||$1==700?$1:0/0):2 \
   via b0, b
amplitude=10000
sigma=100
position=350
fit [90:800] gauss(x) datafile using 1:($2-background($1)) \
   via position, amplitude, sigma
plot datafile using 1:2 with histeps title 'data', \
'' using 1:($2-background($1)) with histeps title 'data-background', \
gauss(x), background(x), gauss(x)+background(x)


baouche wrote:
> 
> This is my best data:
> 
> 50 0.6	
> 100 22	
> 150 20	
> 200 20.4	
> 250 37		
> 300 34.4		
> 350 39.2		
> 400 39.2		 
> 450 32.2 		
> 500 27			
> 550 10.8			
> 600 5.4		
> 650 3.4		
> 700 0.4		
> 750 0
> 
> Regards
> 

-- 
View this message in context: http://old.nabble.com/how-to-draw-Gaussian-shape-with-histogram-tp31029938p31066345.html
Sent from the Gnuplot - User mailing list archive at Nabble.com.