I'm new in gnuplot and my aim is to plot arrows between each data coordinate. My ".dat" file has only two columns, separated by a single tab, where the first is the X and the second is the Y component. The head should be set in the next coordinate.
582.761 -326.288
574.806 -327.915
My command was:
plot 'file.dat' using 1:2 with vectors head filled
I only can obtain the following error message:
Not enough columns for this style
Sorry for the dumb question, but I couldn't understand neither the documentation nor other questions in the same subject.
If you check help vectors you will see that with vectors plotting style requires 4 values.
And if I understand your question correctly I guess you want to plot arrows from one data line to the next data line, correct?
By the expression (x0=x1,x1=$1,x0) you keep the previous x value in x0 and the current value in x1, but you're plotting x0. Same for y0 and y1. And (x1-x0) and (y1-y0) are simply the delta x and delta y values which you need for the with vectors plotting style.
Code:
### vectors from data line to the next
reset session
$Data <<EOD
1 1
2 2
3 5
2 4
1 2
EOD
x1=y1=NaN
plot $Data u (x0=x1,x1=$1,x0):(y0=y1,y1=$2,y0):(x1-x0):(y1-y0) w vectors head filled notitle
### end of code
Result:
Related
I have a data file containing z values (m x n = 2068 x 100), but I fail to find a way to make a surface plot in gnuplot out of that.
In MATLAB the command is straight forward: just surf(M).
The values correspond to readouts over time from a spectrometer, i.e.
wavelength scan1 scan2 scan3 scan4
772.7 3.9609 3.9623 3.9593 3.9643
772.8 2.4688 2.4749 2.4669 2.4689
772.9 2.7233 2.7250 2.7240 2.7270
I understand that gnuplot expects the data to be presented in x,y,z fashion, but my data does not provide that. I'm sorry that I can find no other way to describe what I'm after...
Essentially: the x values are in the first row, but the y values should be the index of the column if that makes sense.
Any help would be much appreciated.
Your data format is halfway between the two formats gnuplot knows about. splot $DATA matrix treats all values as z values (no x or y specified). splot $DATA matrix nonuniform expects the first column to contain y values and the first row to contain x values. You have one column of coordinate data but not one row of coordinate data.
It looks like your x values are evenly spaced, so it would produce a valid surface to ignore them:
splot 'matrix.dat' matrix skip 1 every 1::1
matrix tells gnuplot it is an array of z values
skip 1 tells it to skip the first row, which contains labels rather than z
every 1::1 tells it to read every column starting with column 1 (i.e. skip column 0)
However a much better approach is to draw a separate line for each scan rather than trying to treat it as a surface:
set ylabel "Scan" offset 5
set xlabel "Wavelength" offset 0,-2
set xtics .1 offset 0,-1
unset ytics
unset ztics
splot for [col=2:*] 'matrix.dat' using 1:(col):col title columnhead
I would like to draw a line with plots that contain "jumping" values.
Here is an example: when we have plots of sin(x) for several cycles and plot it, unrealistic line will appear that go across from right to left (as shown in following figure).
One idea to avoid this might be using with linespoints (link), but I want to draw it without revising the original data file.
Do we have simple and robust solution for this problem?
Assuming that you are plotting a function, that is, for each x value there exists one and only one corresponding y value, the easiest way to achieve what you want is to use the smooth unique option. This smoothing routine will make the data monotonic in x, then plot it. When several y values exist for the same x value, the average will be used.
Example:
Data file:
0.5 0.5
1.0 1.5
1.5 0.5
0.5 0.5
Plotting without smoothing:
set xrange [0:2]
set yrange [0:2]
plot "data" w l
With smoothing:
plot "data" smooth unique
Edit: points are lost if this solution is used, so I suggest to improve my answer.
Here can be applied "conditional plotting". Suppose we have a file like this:
1 2
2 5
3 3
1 2
2 5
3 3
i.e. there is a backline between 3rd and 4th point.
plot "tmp.dat" u 1:2
Find minimum x value:
stats "tmp.dat" u 1:2
prev=STATS_min_x
Or find first x value:
prev=system("awk 'FNR == 1 {print $1}' tmp.dat")
Plot the line if current x value is greater than previous, or don't plot if it's less:
plot "tmp.dat" u ($0==0? prev:($1>prev? $1:1/0), prev=$1):2 w l
OK, it's not impossible, but the following is a ghastly hack. I really advise you add an empty line in your dataset at the breaks.
$dat << EOD
1 1
2 2
3 3
1 5
2 6
3 7
1 8
2 9
3 10
EOD
plot for [i=0:3] $dat us \
($0==0?j=0:j=j,llx=lx,lx=$1,llx>lx?j=j+1:j=j,i==j?$1:NaN):2 w lp notit
This plots your dataset three times (acually four, there is a small error in there. I guess i have to initialise all variables), counts how often the abscissa values "jump", and only plots datapoints if this counter j is equal to the plot counter i.
Check the help on the serial evaluation operator "a, b" and the ternary operator "a?b:c"
If you have data in a repetitive x-range where the corresponding y-values do not change, then #Miguel's smooth unique solution is certainly the easiest.
In a more general case, what if the x-range is repetitive but y-values are changing, e.g. like a noisy sin(x)?
Then compare two consecutive x-values x0 and x1, if x0>x1 then you have a "jump" and make the linecolor fully transparent, i.e. invisible, e.g. 0xff123456 (scheme 0xaarrggbb, check help colorspec). The same "trick" can be used when you want to interrupt a dataline which has a certain forward "jump" (see https://stackoverflow.com/a/72535613/7295599).
Minimal solution:
plot x1=NaN $Data u 1:2:(x0=x1,x1=$1,x0>x1?0xff123456:0x0000ff) w l lc rgb var
Script:
### plot "folded" data without connecting lines
reset session
# create some test data
set table $Data
plot [0:2*pi] for [i=1:4] '+' u 1:(sin(x)+rand(0)*0.5) w table
unset table
set xrange[0:2*pi]
set key noautotitle
set multiplot layout 1,2
plot $Data u 1:2 w l lc "red" ti "data as is"
plot x1=NaN $Data u 1:2:(x0=x1,x1=$1,x0>x1?0xff123456:0x0000ff) \
w l lc rgb var ti "\n\n\"Jumps\" removed\nwithout changing\ninput data"
unset multiplot
### end of script
Result:
So I have some data files in format
x y ymin ymax
That I'm plotting with yerrorbars.
Now how would I best add a median of the y values to the plot running over the whole range of x?
UPDATE
I'm also plotting the x axis in logscale which seems to prevent using STATS.
Suppose that your data looks like this:
1 8 6 9
2 6 5 7
3 5 4 8
4 6 5 8
We can use the stats command to find the median. The use is similar to the plot command. Here, we only need to do analysis of the second column, so we will only specify the second column:
stats datafile u 2 nooutput
The nooutput option tells the command not to print the results. If we wish to see the full analysis, we simply omit that specification. By default, the stats command stores its results in variables of the form STATS_*. We can use a different prefix if desired. See help stats for more details.
At this point, we have a variable STATS_median that stores the median of the y values (which is 6 for the sample data). We can now add the median to the graph in one of two ways. First we can simply add a plot specification to the existing plot command:
plot datafile u 1:2:3:4 with yerrorbars, STATS_median
or we can add a line with the set arrow command and then plot just the yerrorbars:
set arrow 1 from graph 0, first STATS_median to graph 1, first STATS_median nohead
plot datafile u 1:2:3:4 with yerrorbars
Here we give the x coordinate in graph units which range from 0 (the left side) to 1 (the right side) and the y coordinate in the first coordinate system which corresponds to the y1 axis. Specifying nohead says to not draw an arrow head. The 1 immediately following set arrow tags this arrow as arrow 1 so that we can change or remove it easily later.
Other options are available. See help arrow for more details.
I want to use gnuplot for real time plotting (Data gets appended to file which I use for plotting and I use replot for real time plotting). I also want to put a label for the latest entry which is plotted. So as to get a idea what is the latest value. Is there a way to do this?
If you are on a unixoid system, you can use tail to extract the last line from the file and plot it separately in whatever way you desire. To give a simple example:
plot\
"data.dat" w l,\
"< tail -n 1 data.dat" u 1:2:2 w labels notitle
This will plot the whole of data.dat with lines and the last point with labels, with the label depicting the value.
There is no need to use the Linux command tail, you can simply do it with gnuplot-only, hence platform-independently.
The principle: while plotting the data, you assign the values of column 1 and 2 to variables x0 and y0, respectively.
After the first plot command, x0 and y0 will contain the last values.
With this, you don't have to load the file a second time for extracting the last values.
For the label plotting, use these values and print the label with a sprintf() expression (check help sprintf).
The construct '+' u ... every ::0::0 is just one way of many ways to plot a single data point.
Data: SO28152083.dat
1 5.1
2 2.2
3 3.3
4 1.4
5 4.5
Script: (works with gnuplot 4.4.0, March 2010 or even with earlier versions)
### plot last value as label
reset
FILE = "SO28152083.dat"
set key noautotitle
set offsets 0.5,0.5,1,1
plot FILE u (x0=$1):(y0=$2) w lp pt 7 lc rgb "red" ti "data", \
'+' u (x0):(y0):(sprintf("%g",y0)) every ::0::0 w labels offset 0,1
### end of script
Result:
I am currently using a script to generate histogram plots, e.g., by doing:
set style histogram cluster gap 4
plot for [COL=2:10] 'example.dat' u COL:xticlabels(1) title columnheader(COL)
Now I wish to add the y-values (numbers) above the bars in the histogram but adding w labels gives the 'Not enough columns for this style' error.
plot for [COL=2:10] 'example.dat' u COL:xticlabels(1) title columnheader(COL), \
for [COL=2:10] 'example.dat' u COL title '' w labels
Is it possible to add y-labels using the histogram style?
Note: I know that there are examples for plotting with boxes. I wish to make this work with the histogram style if possible.
Here's a test datafile I came up with:
example.dat
hi world foo bar baz qux
1 2 3 4 5 6
4 5 7 3 6 5
Here's the script I used to plot it:
set yrange [0:*]
GAPSIZE=4
set style histogram cluster gap 4
STARTCOL=2 #Start plotting data in this column (2 for your example)
ENDCOL=6 #Last column of data to plot (10 for your example)
NCOL=ENDCOL-STARTCOL+1 #Number of columns we're plotting
BOXWIDTH=1./(GAPSIZE+NCOL) #Width of each box.
plot for [COL=STARTCOL:ENDCOL] 'example.dat' u COL:xtic(1) w histogram title columnheader(COL), \
for [COL=STARTCOL:ENDCOL] 'example.dat' u (column(0)-1+BOXWIDTH*(COL-STARTCOL+GAPSIZE/2+1)-0.5):COL:COL notitle w labels
Each cluster of histograms takes a total width of 1 unit on the x axis. We know how many widths we need (the number of boxes +4 since that is the gapsize). We can calculate the width of each box (1/(N+4)). We then plot the histograms as normal. (Note that I added with histogram to the plot command).
According to the builtin help, labels require 3 columns of data (x y label). In this case, the y position and the label are the same and can be read directly from the column COL. The x position of the first block is centered 0 (and has a total width of 1). So, the first block is going to be located at x=-0.5+2*BOXWIDTH. The 2 here is because the gap is 4 boxwidths -- two on the left and 2 on the right. The next block is going to be located at -0.5+3*BOXWIDTH, etc. In general, (as a function of COL) we can write this as
-0.5+BOXSIZE*(COL-STARTCOL+1+GAPSIZE/2)
We need to shift this to the right by 1 unit for each additional block we read. Since each block corresponds to 1 line in the data file, we can use pseudo-column 0 (i.e. column(0) or $0) for this since it gets incremented for each "record/line" gnuplot reads. The 0th record holds the titles, the first record holds the first block. Since we want a function which returns 0 for the first record, we use column(0)-1. Putting it all together, we find that the x-position is:
(column(0)-1-0.5+BOXSIZE*(COL-STARTCOL+1+GAPSIZE/2))
which is equivalent to what I have above.