pro routine_filepath_no_params
   compile_opt idl2

   print, 'I''m called from a program in the file: ' + routine_filepath()
end

When I run this program, I get:

IDL> routine_filepath_no_params
I'm called from a program in the file: /home/mpiper/VIS/IDL/8/22/demos/src/routine_filepath_no_params.pro

Jim Pendleton, for example, has found this helpful in determining whether a program is being run from a SAVE file or a PRO file. I’ve used it to save a visualization to a PNG file with the same base name as the PRO file in which it’s generated.

(This is, I think, my last 8.2.2 post before 8.2.3 comes out next week!)

The big themes for IDL in 2013 are:

• visualization
• file access

In the IDL releases this year (8.2.2 in February, 8.2.3 in May and 8.3 this fall), we’re trying to tie development (including improvements, new features and bugfixes) to these themes. Outside issues arise and are addressed, but we’re trying to prioritize stories that fit these themes. So far, this has included new (New) Graphics routines like SCATTERPLOT, BOXPLOT, and soon, BUBBLEPLOT and VOLUME, as well as continued improvements to the performance and usability of NG. For file access, we’ve updated our HDF4, HDF-EOS and CDF libraries, and updates to netCDF, HDF5 and GRIB are on the way.

Looking at the 2013 releases as a whole, I think we’re making good progress in addressing these themes.

(If I get egged on enough, I’ll talk about what we’re thinking about for IDL in 2014, too.)

• BUBBLEPLOT
• VOLUME
• FILE_ZIP
• FILE_UNZIP
• FILE_GZIP
• FILE_GUNZIP
• FILE_TAR
• FILE_UNTAR
• ZLIB_COMPRESS
• ZLIB_UNCOMPRESS
• IDLffVideoRead class
• QUERY_VIDEO
• READ_VIDEO
• WRITE_VIDEO
• TERMINAL_SIZE

BUBBLEPLOT has been an early favorite around VIS. Here’s a sample from Eddie Haskell, the developer who wrote it (click to embiggen):

I’ll post more information on these routines, as well as the rest of what’s included in 8.2.3, on the release date.

IDL> p = plot([0,1], 'r')

Select the plot by clicking the mouse in the interior of the plot frame. To move the plot, click the frame and drag it. To resize the plot, click and drag a manipulator on the corner or middle of the frame.

Once you’ve moved and/or resized a plot, you can programmatically retrieve its new location and size from the POSITION property. For example, I moved and resized my plot to give:

IDL> print, p.position
      0.12656254      0.47788962      0.54761025      0.88085938

Note that these values are in normalized coordinates (x and y range over a unit interval); the first two values give the (x,y) coordinate of the lower left corner of the plot frame, while the last two values give the coordinate of the upper right corner of the plot frame.

In IDL 8.2.2, we modified the POSITION property so that you can also programmatically set the size and position of a plot; e.g.:

IDL> p.position = [0.50, 0.45, 0.90, 0.90]

The result is a plot in the upper left corner of the window:

Start with a 4 x 5 array of numbers:

IDL> a = round(randomu(seed, 4, 5) * 20.0)
IDL> print, 'Original array:', a, format='(a,/,4(i))'
Original array:
           8           6          14          10
           4           9          18           5
           1          11          13          18
           8           9          11           9
           3          19           4          16

Use COLSORT to perform a reverse sort on column index 1 (the second column) and extend the sort to the other columns in the array:

IDL> sort_index = 1
IDL> b = colsort(a, sort_index, /reverse_sort)

Check the result:

IDL> print, 'Sorted (descending) array:', b, format='(a,/,4(i))'
Sorted (descending) array:
           3          19           4          16
           1          11          13          18
           8           9          11           9
           4           9          18           5
           8           6          14          10

This program could be extended to apply to rows and to arrays of higher dimensionality.

The ubiquitous WHERE function can be used to quickly locate values in an array. However, you can’t directly search for the location of IEEE NaN (not a number) and Inf (infinity) values; to do so, you need the FINITE function. Here’s an example.

Start with a simple array:

IDL> a = findgen(5, 2)
IDL> print, a
     0.000000      1.00000      2.00000      3.00000      4.00000
      5.00000      6.00000      7.00000      8.00000      9.00000

and add NaN values at up to three random locations:

IDL> i = floor(randomu(seed, 3)*n_elements(a))
IDL> a[i] = !values.f_nan
IDL> print, a
     0.000000      1.00000      2.00000      3.00000          NaN
          NaN      6.00000      7.00000          NaN      9.00000

OK, so where are the NaNs located? By eye, I can see where they are (indices 4, 5 and 8), but to identify them programmatically, use WHERE with FINITE and “~”, the logical not operator:

IDL> i_nan = where(~finite(a), /null)
IDL> print, i_nan
           4           5           8

Check!

• T-9: A Rapid Cloud Mask Algorithm  for Suomi NPP VIIRS Imagery EDRs (Piper) [PDF, 2.5 MB]
• W-37: ENVI Services Engine: Earth and Planetary Image Processing for the Cloud (Harris)

If you’re attending this conference, please visit our posters and say hello!

The IDL 8 (a.k.a. New) Graphics CURRENT keyword got a useful update in IDL 8.2.2: instead of being a Boolean, it now accepts a window reference, which allows me to place a plot in a specific window. For example, if I make two empty windows, W1 and W2:

w1 = window(window_title='Window #1')
w2 = window(window_title='Window #2')

and I want to ensure that a new plot goes into the first window, W1, I can set the CURRENT keyword like so:

p = plot(/test, current=w1, title='I''d like this to be in Window #1')

Check!

Prior to IDL 8.2.2, the SetCurrent method would also do the trick, but I think this syntax is nicer.

That’s IDL color table 15, Stern Special.

(Click to embiggen.)

From the WSA-Enlil Solar Wind Prediction page, a description of this plot:

The top row plots show predictions of the solar wind density. The bottom row plots show solar wind velocity. The circular plots on the left are a view from above the North Pole of the Sun and Earth, as if looking down from above. The Sun is the yellow dot in the center and the Earth is the green dot on the right. Also shown are the locations of the two STEREO satellites. These plots often depict spiral structures, due to solar rotation. The wedge-shaped plots in the center provide a side view, with north at the top and south at the bottom. The graphs on the right show the model predictions for the time evolution of density and velocity at the locations of Earth and of the two STEREO spacecraft. The yellow vertical line is in sync with the movies on the left, so it is possible to see how values of density and velocity correspond to particular solar wind structures.

Thanks, George! (Are we getting hit by a solar storm at 6 pm today?)

If you’ve done something cool with IDL that you’d like to share, please let me know!

Note: Dr. Millward’s article was also highlighted recently in the “Research Spotlight” section of Eos, Vol. 94, No. 17, 23 April 2013.