I try to reproduce a simple histogram with Gnuplot with the simple macro:
reset
n=9 #number of intervals
width=1 #interval width
hist(x,width)=width*floor(x/width)
set terminal pngcairo size 800,500 enhanced font 'Verdana,14'
set output "test.png"
set boxwidth width
set style fill transparent solid 0.5 border #fillstyle
set xrange [*:*]
set yrange [0:2.]
set xlabel "x"
set ylabel "Freq."
plot "const.dat" u (hist($1,width)) smooth freq w boxes lc rgb "orange" notitle
whit the follow data:
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
Now I like to understand how the hist(x,width) works in the sense:
hist(x,width)=width*floor(x/width)
works with every numbers taking the width=1 and then:
hist(1.1,1)=1*floor(1.1/1)=1
and so on, right?
Now (hist($1,width)) take all the elements in the columns and applay the hist function to everyone.
And I can be able to make the follow plot with the macro above:!
Question:
If I use (hist($1,width)):(1.0) I Don't understand whit the plots change as all the elements stay in one single boxes (from 0.5 to 1.5) ?
In the first case you specify only a single column in the using statement. Since you need at least two (x and y-value), the specified value (your hist(...)) is used as y-value and the row number as x-value. The statement smooth frequency works such, that it takes all points with the same x-value and sums up the corresponding y-values. In your first example you have no equal x-values since the row number is used.
In the second example, you use the hist(...) value as x-value, which is 1 for all rows. The y-value is 1.0. So you get a single box at x=1 and y=8 (the number of rows).
Related
I have the following 'data.dat' file:
# x y z radius
-1.64905083 -1.14142799 -2657.88232 177.358566
-449.735321 416.586914 -2865.25366 10.0000000
178.955292 -256.291138 -2856.96069 89.9588394
-336.942322 184.932343 -2839.22876 90.6131058
-443.635315 -80.0183029 -2863.29077 70.7404404
236.385406 349.893188 -2901.33984 10.0000000
485.313416 -366.513947 -2868.35083 10.0000000
with the positions of the spheres and their radii.
My file.p reads:
set terminal png size 500,500
set output 'file.png'
set multiplot
set xrange [-1000:1000]
set yrange [-1000:1000]
set zrange [-3000:-2500]
splot "data.dat" using 1:2:3:4 ps variable pt 7
splot -(3000**2-x**2-y**2)**(0.5)
but the dots that gnuplot provides me are much bigger.
I understand that it is because ps yields points that are radius times bigger than the normal size.
Meaning that ps does not allow to set the radius of the dots, but rather how many times bigger it is than the normal points.
How can I set the radius of the points please ?
Use "with circles" rather than "with points pt 7".
From the manual:
gnuplot> help with circles
The `circles` style plots a circle with an explicit radius at each data point.
The radius is always interpreted in the units of the plot's horizontal axis
(x or x2). The scale on y and the aspect ratio of the plot are both ignored.
If the radius is not given in a separate column for each point it is taken from
`set style circle`. In this case the radius may use graph or screen coordinates.
Many combinations of per-point and previously set properties are possible.
For 2D plots these include
using x:y
using x:y:radius
using x:y:color
using x:y:radius:color
using x:y:radius:arc_begin:arc_end
using x:y:radius:arc_begin:arc_end:color
By default a full circle will be drawn. It is possible to instead plot arc
segments by specifying a start and end angle (in degrees) in columns 4 and 5.
A per-circle color may be provided in the last column of the using specifier.
In this case the plot command must include a corresponding variable color
term such as `lc variable` or `fillcolor rgb variable`.
I have already asked about vector fields in here. Now I want to know a bit more about it.
How can I make it so that each arrow has the same fixed length and define the magnitude of the value by color?
And is it still not possible to plot streamlines in gnuplot? If possible, how can I do that?
For now I have this and need to upgrade it.
set term pngcairo
set title 'Navier-Stokes Equation'
set terminal png size 1280,720
set output 'vec.png'
plot 'vec' u 1:2:($3/$5):($4/$5) w vec t 'Vector Field'
UPDATE
Thanks to #theozh I've got what I wanted. I want to share my result as it could be useful for someone else.
Now I use these instructions to plot my vector field.
reset session
set size square
set palette rgb 33, 15, 10
set term pngcairo
set title 'Navier-Stokes Equation'
set terminal png size 1280, 720
set output 'vec.png'
plot 'vec.dat' u 1:2:(0.08*$3):(0.08*$4):(sqrt($3**2+$4**2)) w vec lw 2 lc palette notitle
About the same length: simply normalize your vectors.
About the color:
you can add a "column" and the end. The last column will define the color according to a palette.
I don't know about streamlines (what exactly they are and how to possibly realize them).
With the example script:
Script: (Edit: define function for length L() to make plot command shorter and clearer.)
### plot with normalized/scaled vectors
reset session
set size square
set samples 25
set palette rgb 33,13,10
set key noautotitle
Scale = 0.5
L(colX,colY) = sqrt(column(colX)**2+column(colY)**2)
plot [-5:5] '++' u 1:2:(Scale*$1/L(1,2)):(Scale*$2/L(1,2)):(L(1,2)) w vec lc palette
### end of script
I’m trying to plot multiple Gaussian functions on the same graph with Gnuplot, which is quite a simple thing. The problem is that the peaks do not overlap and I get the following result that looks like they have different peaks, which they don’t. How can I fix this?
First, it helps to understand how gnuplot generates plots of functions (or really how any computer program must do it). It must convert a continuous function into some kind of discrete representation. The mathematical function to be plotted is evaluated at various points along the independent (x) axis. This creates a set of (x,y) points. A line is then drawn between these points (think "connect the dots"). As you might imagine, the number of discrete samples used affects how accurately the curve is represented, and how smooth it looks.
The problem you have noticed is that the default sample size in gnuplot is a bit too low. The default (I believe) is 100 samples across the visible x-axis. You can adjust the number of samples (to 1000, for example) with
set samples 1000
I have made some example plots of gaussians to illustrate this point. (I made a rough estimate of your gaussian parameters.) Each plot has a different number of samples:
Notice how the lines get too jagged if the sample size is too low. Even the default value of 100 is too low. Setting to 1000 makes it plenty smooth. This is probably more than it needs to be, but it works. If you're using a terminal that generates a bitmap image (e.g. PNG), then you shouldn't need more samples than you have width in pixels used for the x-axis plot area. If you're generating vector based output, then just pick something that "looks right" for whatever you are using it in.
See the question Gnuplot x-axis resolution for more.
By the way, the code to generate the above examples is:
set terminal pngcairo size 640,480 enhanced
# Line styles
set style line 1 lw 2 lc rgb "blue"
set style line 2 lw 2 lc rgb "red"
set style line 3 lw 2 lc rgb "yellow"
# Gaussian function stuff
set yrange [0:1.1]
set xrange [-20:20]
gauss(x,a) = exp(-(x/a)**2)
eqn(a) = sprintf("y = e^{-(x/%d)^2}", a)
# First example (default)
set output "example1.png"
set title "100 samples (default)"
plot gauss(x,8) ls 1 title eqn(8), \
gauss(x,2) ls 2 title eqn(2), \
gauss(x,1) ls 3 title eqn(1)
# Second example (too low)
set output "example2.png"
set title "20 samples (too low)"
set samples 20
replot
# Third example (plenty high)
set output "example3.png"
set title "1000 samples (plenty high)"
set samples 1000
replot
I want my legend to be inside the plot and therefore, I want to increase the yRange by a fixed amount. However, that fixed amount should be %20 of maximum y amount.
Some graphs I plot are percentages and some of them are just values. Hence, I cannot use the same range for all, but I need to increase the yRange so that legend won't overlap with the plot itself.
How can I do it?
You can use set offsets to achieve this. Use
set offsets 0,0,graph 0.2,0
to expand the upper graph boundary by 20% of the total, automatically calculated height. This might be a bit more then 20% of the maximum y-value because gnuplot first expands to the next major tics. If you want to have exactly 20% of the maximum, you must use
set autoscale yfixmax
set offsets 0,0,graph 0.2,0
If you have Gnuplot version 4.6 then you can leverage stats to get the max/min of the y column in your data file and then use that to augment the yrange. Assuming your y data is in column 1 of your data file:
stats 'datafile' using 1
y_max_augmented = STATS_max + STATS_max * 0.2
set yrange [STATS_min:y_max_augmented] # you may use any other value in place of STATS_min
I'm using gnuplot to plot three dimentions of data using pm3d. I'm trying to plot the number of times an event occurs (z value) with respect to the day of the year (x value) and hour of the day (y value).
Using pm3d works great for up to a range of 600 (rought 2 years of data). However, the points begin to overlap each other when a wider range is required.
I believe this is related to the fact that gnuplot isn't stretching the plot to the full size specified in set terminal. I haven't however been able to find a setting that controls this directly.
the script I'm using:
set terminal png size 10000, 1000
set output "%s_plot.png"
set title "%s's"
set ytics 1,1
set xtics 1
set xrange[0:%s]
set yrange[0:23]
set cbrange[0:%s]
set pm3d map
set palette defined (0 "white", 1 "blue", 31 "red")
splot '%s.data'
aspect of the plot for a range of [0:1000] in x:
aspect of the plot for a range of [0,100] in x:
(the images above are just snippets of the whole thing)
What can I do to remedy this? Perhaps the solution is manually setting the points (squares) to have a fixed width.
Thanks.
For the kind of plot that you want, I would replace your last line with:
plot '%s.data' matrix with image