Histogram with new -w cyclic option

Q&A
1

Hi ,

I have a file containing 1 column with absolute times :

> cat test.txt
1980-01-09T09:00:00
1980-01-29T03:00:00
1980-02-14T06:00:00
...
2016-03-13T15:00:00
2016-09-17T15:00:00
2016-10-13T06:00:00
...

I want to plot an histogram with a frequency in y-axis and months in x-axis using this command :

gmt begin test01
gmt histogram -JX10c -Ttest.txt -Bxaf+l"Months" -Byaf+l"Frequency"+u"%" -D+r -N0 -Z1 -wa -Glightblue -Wthinnest,black
gmt end show

But it just gets stuck (no error, just infinite loop) :

histogram [DEBUG]: History: Process -JX10c
histogram [INFORMATION]: Processing input table data
histogram [DEBUG]: gmtapi_init_import: Passed family = Data Table and geometry = Volume
histogram [DEBUG]: gmtapi_init_import: Added 0 new sources
histogram [DEBUG]: Object ID 0 : Registered Data Table Stream 7fff88bcfe50 as an Input resource with geometry Volume [n_objects = 1]
histogram [DEBUG]: gmtapi_init_import: Added stdin to registered sources
histogram [DEBUG]: GMT_Init_IO: Returned first Input object ID = 0
histogram [DEBUG]: GMT_Begin_IO: Mode value 1 not considered (ignored)
histogram [DEBUG]: GMT_Begin_IO: Initialize record-by-record access for Input
histogram [DEBUG]: gmtapi_next_io_source: Selected object 0
histogram [INFORMATION]: Reading Data Table from Standard Input stream
histogram [DEBUG]: GMT_Begin_IO: Input resource access is now enabled [record-by-record]

If I add -R0/12/0/100 it doesn’t solve the bug.

Thanks

2

I think it will work if you just do test.txt rather than -Ttest.txt. It is trying to read the data from standard input rather than your text file.

3

You should be able to instead use -T1 to get annual intervals

4

Thanks Meghan,

So what’s the -T1 's for ?

5

-T[min/max]int is required to set the interval for the bins (leaving off min/max implies they can be read from -R).

In your example, using -wa reformats your input data to all be in the range 0 - 12, so -T1 will then bin them every integer which is the same as binning by months thanks to the new -w option. Similarly -T3 could be used to bin by quarter.

p.s. you can use gmt convert @test.txt -wa > output.txt to see what -wa is doing.

1 Like
6

More practical question … how do I shift the plot to be centered on Winter ?
-wa/[phase] doesn’t work

-E1+o6 doesn’t cycle

7

You can use -R to control the center value. For example: -R-5/7/0/8 would set the first bin to August.

8

Awesome.
I didn’t think about assigning negative values.
Puuurfect :slight_smile:

9

Satisfying result :

  1. Transform indices from file to absolute time :
# The data of interest are in the first column of event_index.txt
# The time-step in my original file is 3 hours
gmt math -o0 -foT -C0 event_index.txt 3 MUL 3 SUB --TIME_EPOCH=1980-01-01 --TIME_UNIT=h = test.txt
  1. Plot the annual frequency histogram centered on winter :
# First month is August, the last is July
gmt begin test01 png
gmt histogram -R-5/7/0/20 -JX10c test.txt  -T1 -BWSen -Bxa1Of1O+l"Months" -Byaf+l"Frequency"+u"%" -D+r -Z1 -wa -Glightblue -Wthinnest,black --FORMAT_TIME_PRIMARY_MAP=c
gmt end

test01
test011427Ă—1366 21.4 KB

1 Like
10

Very nice! It confirms the old Wessel saying “There is nothing GMT cannot do as long as we code up what it is we want it to do”.

11

Indeed !
However the -N option is weird … (I don’t need it, but you might want to have a look at how it’s plotted)

12

We have tests that use -N that looks fine, but that predates -w. If you have a strange example, then please share.

13

Taking the example above,

  • I removed -R (starts in January)
  • I added -N0

test01
test011427Ă—1366 23.8 KB

14

I will reluctantly agree with you that this is not the expected curve. Could you please post test.txt so I can reproduce?

15

here you go :slight_smile:

test.txt (9.8 KB)

16

thank you - will try to give it a test this weekend.