TVMAP cheat sheet
This cheat sheet shows some of the most useful features of TVMAP that can be quickly tested at the command line (IDL prompt)... and used in your own programs.
Default behavior
Check:
DATA = DIST(30,20) TVMAP, DATA TVMAP, DATA, /SAMPLE, /CBAR
This is the same as (showing the implicit lon/lat range associated with the data):
DATA = DIST(30,20) LON =-180. + findgen(30)*12 + 6. ; box center LAT = -90. + findgen(20)* 9 + 4.5 ; box center TVMAP, DATA, lon, lat
Zooming
To zoom, there is no need to cut the data to the window size, just use the LIMIT keyword. Compare:
TVMAP, DATA, LON, LAT, /GRID, /CONTINENTS TVMAP, DATA, LON, LAT, /GRID, /CONTINENTS, LIMIT=[-10,0.,60.,25.]
Note that if you do not pass the LON and LAT associated to DATA, only the map is zoomed. Compare:
TVMAP, DATA, /GRID, /CONTINENTS, LIMIT=[-10,0.,60.,25.] TVMAP, DATA, LON, LAT, /GRID, /CONTINENTS, LIMIT=[-10,0.,60.,25.]
It is strongly recommended to specify LON and LAT all the time.
LIMIT keyword tip
The following can be handy in a program, where you sometimes need to set the LIMIT. Setting LIMIT to 0 is the same as not setting it:
TVMAP, DATA, LIMIT=0
Out-Of-Range data and Colorbar
with a (default) white box
To indicate data below (above) a specific value, use MIN_VALID (MAX_VALID):
TVMAP, DATA, MIN_VALID=5., /SAMPLE, /CBAR
with a Triangle instead of a box
TVMAP, DATA, MIN_VALID=5., /TRIANGLE, /sample, /CBAR
with a non-white box
Use BotOutOfRange (TopOutOfRange) to specify the color for data below MIN_VALID (above MAX_VALID):
TVMAP, DATA, BOTOUTOFRANGE=!myct.gray50, MIN_VALID=5., /SAMPLE, /CBAR
with a non-white triangle
Combine Triangle and BotOutOfRange:
TVMAP, DATA, BOTOUTOFRANGE=2, MIN_VALID=5., /TRIANGLE, /CBAR
without any indication in the colorbar
Use a negative color index:
TVMAP, DATA, BOTOUTOFRANGE=-2, MIN_VALID=5., /SAMPLE, /CBAR
Tip: To denote out-of-range data with WHITE, but without a box or triangle in the colorbar, you must use the color index -17. White is available as index 0 and 17 with the standard set of colors of Gamap !MyCT.
TVMAP, DATA, BOTOUTOFRANGE=-17, MIN_VALID=5., /CBAR, /SAMPLE
Conditional insertion of triangles
Here is a wrapper that automatically add a triangle if, and only if, there is out of range data:
PRO WRAP_TVMAP, data, lon, lat, range, BOOR=BOORi, TOOR=TOORi, _extra=e
; Default values
; ---------------------------
minvalid = range[0] & maxvalid = range[1] & triangle = 1
BOOR = keyword_set( boori ) ? boori : !myct.bottom
TOOR = keyword_set( toori ) ? toori : !myct.bottom+!myct.ncolors
; Check for out-of-range data
; ---------------------------
cr = range[sort(range)]
nim = min(data, max=xam, /NaN)
if ~ (nim lt cr[0] or xam gt cr[1]) then $
UNDEFINE, minvalid, maxvalid, toor, boor, triangle
; Map plot
; ---------------------------
TVMAP, data, LON, LAT, /cbar, /continents, /sample, $
mindata=range[0], maxdata=range[1], $
cbmin=range[0], cbmax=range[1], $
; denote out-of-range:
BotOutOfRange = BOOR, TopOutOfRange=TOOR, Triangle=triangle, $
min_valid=minvalid, max_valid=maxvalid, $
_extra = e
return
end
NaN data
To deal with NaN, you can set them to a very low or high value and use the MIN/MAX_VALID keywords. But you can also directly use the NAN_COLOR keyword (default to 0):
DATA[where(data gt 6)]=!values.f_nan TVMAP, DATA, nan_color=!myct.orange
GRIDS
One or more GRID without DATA
If you just want to plot one grid, you can use the CTM_MAPGRID routine from GAMAP. For a more general approach, use MAP_GRID, like this (several tips at once!):
; no grid MAP_SET, /ORTHOGRAPHIC, 65., -15., 0., /isotropic, COLOR=!MYCT.BLACK ; 1st grid (not global) lats = -78 + findgen( 79 )*2 lons = -180 + findgen( 121 )*3 MAP_GRID, LATS=LATS, LONS=LONS, glinestyle=0, COLOR=!MYCT.black ; 2nd grid (automatic generation of LONS / LATS vectors from ranges ; and steps) lon=[-30, 30] & lat= [34, 70] dlon=1 & dlat=0.5 lats = lat[0] + findgen( fix((lat[1]-lat[0])/dlat +1) )*dlat lons = lon[0] + findgen( (lon[1]-lon[0])/dlon +1 )*dlon MAP_GRID, LATS=LATS, LONS=LONS, glinestyle=1, COLOR=!MYCT.red, glinethick=2 ; Continents MAP_CONTINENTS, /COAST, /COUNTRIES, COLOR=!myct.blue, MLINETHICK=2
Control the GRID - (1) with /GRID
Setting /GRID, TVMAP will call MAP_GRID. Then you can pass keywords to MAP_GRID through the _EXTRA facility, like specifying the location of the grid lines (see MAP_GRID documentation for more on those keywords) or black/white box axes:
tvmap, data, /contin ; no grid tvmap, data, /contin, /grid ; grid tvmap, data, /contin, /grid, /BOX_AXES ; passsing MAP_GRID keywords tvmap, data, /contin, /grid, LONS=-165., LATS=[-72.,-10,5,40] ; passsing MAP_GRID keywords
But if the MAP_GRID keyword is also a MAP_SET keyword, then MAP_SET will trigger a second call to MAP_GRID, and you end up with two grids. So you cannot pass the following MAP_GRID keywords without having two grids (although the two grids may be identical, and you may not notice!). For example:
tvmap, data, /contin, /grid, glinestyle=2 ; two grids problem
; list of keywords common to MAP_SET and MAP_GRID (do not use them with TVMAP, /GRID): GLINESTYLE GLINETHICK LABEL LATALIGN LATDEL LATLAB LONALIGN LONDEL LONLAB
So, this method (grid keywords along /GRID) is useful but limited to keywords unknown to MAP_SET.
However, since v2.12 of GAMAP, you can use /GRID and specify the grid \emph{spacings} with DLON and DLAT keywords. The GXLABELS and GYLABELS can also be used to label every n-th gridlines (or none if zero). Compare the following to see how things work:
data=dist(40,40) tvmap,data tvmap,data, /grid tvmap,data, /grid, dlat=8, dlon=10 tvmap,data, /grid, dlat=4, dlon=5, gxlabels=0, gylabels=0 tvmap,data, /grid, dlat=4, dlon=5, gxlabels=5, gylabels=4
Control the GRID - (2) with GRID=0
Not setting /GRID (or setting GRID=0), you can still trigger a call to MAP_GRID through MAP_SET, by using one of the grid keyword accepted by MAP_SET:
TVMAP, data, lon, lat, /contin, GLINESTYLE=0
To pass other grid keyword (those not accepted by MAP_SET), you must use the E_GRID keyword:
TVMAP, data, lon, lat, /contin, limit=[0,-160.,70,-30], latdel=8, londel=10, &
e_grid={box_axes:1}, nogxlabels=1, nogylabels=1
Note the use of NoGXLabel to leave control of the grid labels to MAP_GRID. This method gives you more control, since you can use all grid keywords, directly or with E_GRID.
Concrete example : plotting the GEOS-Chem grid box with TVMAP
You must pass the grid edges with LATS and LONS keywords to MAP_GRID. If the grid info structure associated with your data is called GridInfo, you will go with:
tvmap, data, xlon, ylat, /sample, &
lats=gridinfo.yedge, lons=gridinfo.xedge, /grid
You can also improve the rendition with color:
tvmap, data, xlon, ylat, /sample, lats=gridinfo.yedge, lons=gridinfo.xedge, /grid, gcolor=!myct.gray15
However, if you want to modify other details of the grid, you must use the E_GRID keyword but not GRID. For example, the LINESTYLE of the grid:
tvmap, data, xlon, ylat, /sample, glinestyle=5, e_grid={lats:gridinfo.yedge, lons:gridinfo.xedge, color:=!myct.gray15}
What happens: there is no call to MAP_GRID in TVMAP (because we do not use /GRID), but instead a call to MAP_GRID triggered by MAP_SET (because we use GLINESTYLE).
FAQ : help, my plot has TWO grids!
QUESTION: I try to modify some GRID features when calling TVMAP and end up with 2 grids. What's happening?
ANSWER: MAP_GRID can be triggered by :
- TVMAP if /GRID is set
- MAP_SET if grid related keywords accepted by MAP_SET are used.
You used both /GRID and a grid keyword recognized by MAP_SET.
Solution: do not use the /GRID keyword. See recommended method #2.
Control TVMAP settings from CTM_PLOT and/or GAMAP
Most of TVMAP keywords can be set when calling GAMAP or CTM_PLOT (thanks to the _extra facility of IDL):
gamap, file=ftest, 'anthsrce', dlon=2, dlat=2, lats=0.5, lons=-130.5,/usa, format='(f5.1)', &
gylab=4,gxlab=10, min_valid=0.00000001
However, sometimes, a TVMAP keyword must be set with a different keyword in CTM_PLOT! For example, use YRANGE with CTM_PLOT to specify the MAXDATA passed to TVMAP:
YRANGE of CTM_PLOT <==> MAXDATA of TVMAP
Similarly, ON/OFF TVMAP keywords can be turn ON by default in CTM_PLOT or GAMAP, while they are OFF by default when calling TVMAP. You need to explicitly turn them OFF if you want them so. For example, by default, ISOTROPIC is off when calling TVMAP, but on when calling CTM_PLOT.
; unset default /isotropic CTM_PLOT, ...., ISOTROPIC=0
Map projections
To get a list of ALL available map projections
Look into the IDL manual, or:
MAP_PROJ_INFO, PROJ_NAMES = NAMES PRINT, TRANSPOSE(NAMES)
which opens programming possibilities.
Modifying TVMAP default map projection
You do not need to hack into TVMAP. Simply pass relevant MAP_SET keywords to TVMAP. You can overwrite MPARAM or/and LIMIT, or pass a new projection keyword like /LAMBERT.
DATA = DIST(30,20) lon = -180. + findgen(30)*12 + 6. ; box center lat = -90. + findgen(20)*9 + 4.5 ; box center TVMAP, data, lon, lat, rectangle=0, GxLabels=0, /GOODES, /HORIZON
For a more elaborate projection, focusing on the USA,
Limit = [40, -130, 45, -142, 40, -65, 24, -100] ConUS_Y = 37 ConUS_X = -97 TVMAP, data, lon, lat, /CONTINENTS, MPARAM=[CONUS_Y, CONUS_X,0], LIMIT=LIMIT, /LAMBERT, /USA
or North America,
Limit = [40, -140, 85, -142, 40, -50, 10, -100] ConUS_Y = 45 ConUS_X = -97 TVMAP, data, lon, lat, MPARAM=[CONUS_Y, CONUS_X,0], LIMIT=LIMIT, /LAMBERT, /COUNTRIES, /CONTINENTS
or Europe:
Limit = [40, -15, 75, 20, 40, 40, 30, 20] ConUS_Y = 57 ConUS_X = 12 TVMAP, data, lon, lat, MPARAM=[CONUS_Y, CONUS_X,0], LIMIT=LIMIT, /LAMBERT, /COUNTRIES, /CONTINENTS
Using TVMAP and MULTIPANEL
simple way
Everything is handled automatically when only using TVMAP:
multipanel, 4 for k=0,3 do tvmap, data multipanel,/off
But if it is combined with other type of plot, here is the procedure:
multipanel, 4 tvmap, data multipanel, position=p plot, findgen(12), color=!myct.black, position=p multipanel, /advance, /noerase tvmap,data tvmap,data multipanel,/off
advanced combination
Using /NOERASE and /ADVANCE in multiple calls to MULTIPANEL, let you arrange your plots however you like. Try something like this:
pro test
data = dist(20,30)
; set a 2x2 panels
multipanel, rows=2, cols=2
; set counterclockwise ordering
!p.multi[4] = 1
tvmap, data, title='plot 1'
tvmap, data, title='plot 2'
; switch to 4x3 panels, and back to clockwise ordering
multipanel, cols=4, rows=3, /noerase
!p.multi[4] = 0
for k=3, 7, 2 do begin
multipanel, /advance
multipanel, /advance
tvmap, data, title='plot ' + strtrim(k, 2)
tvmap, data, title='plot ' + strtrim(k+1, 2)
endfor
; reset
multipanel, /off
return
end
I let you figure out the unique colorbar (hint: use OMargin in the first call to MULTIPANEL).
Overplot lines or string
The active plot must be the last map projection, and not the next plot to come (which is the default). To stay on the map, use /NOADVANCE:
tvmap, dist(20, 20), /contin, /noadvance LON=[-36., 54.] & LAT=[2., 74.]
plots, [LON[0], LON[1], LON[1], LON[0], LON[0]], &
[LAT[0], LAT[0], LAT[1], LAT[1], LAT[0]], &
color=!myct.black, thick=2, _extra=e
Same story to use XYOutS for string.
About the SCALE keyword
Both MAP_SET and TVIMAGE accept the SCALE keyword. The IDL routine DEVICE (when using PS or PRINTER device) accepts the SCALE_FACTOR keyword. So be careful when using that _EXTRA facility! Note that TVMAP has two `scale' keyword for that purpose:
ScaleMapSet to specify the MAP_SET SCALE keyword ScaleMapImage to specify the TVIMAGE SCALE keyword
If you have any doubt try your keywords on this example, and add explicit keywords if needed:
pro my_routine, _extra=e open_device, _extra=e tvmap, dist(12,12), _extra=e close_device end
Known Issue(s)
Bug with MAX_VALID
Try:
DATA = DIST(20,20) Window,1 & TVMAP, DATA, MAX_VALID=20., /CBAR
This gives a wrong plot if X > MAX(DATA) and MAXDATA keyword is not used. The fix is to use both:
Window,2 & TVMAP, DATA, MAX_VALID=20., MAXDATA=20., /CBAR
--phs 13:14, 13 March 2012 (EDT)