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IDL 8.0 Graphics: A Primer in the new Graphical System

This primer delves into the new graphical system in IDL 8.0, highlighting the new graphics, plotting, mapping, contour, and vector routines, as well as the ability to do streamlines. Learn about the changes, annotations, color schemes, symbol storage, and dynamic plot changes. Additionally, understand the bugaboos with the new routines and learn functional tips like setting properties dynamically. Discover the enhancements in the new system compared to the old direct graphics, making your plotting more dynamic and efficient.

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IDL 8.0 Graphics: A Primer in the new Graphical System

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  1. IDL 8.0 Graphics: A Primer in the new Graphical System Jonathan Fairman UAH Atmospheric Science 3/4/11 and 3/7/11 Short Course

  2. What’s new in IDL 8.0? • New graphics system • New plotting routines • New mapping routines • New contour routines • New vector routines • Ability to do streamlines!

  3. Overview • New System Introduction • Changes to PLOT • Annotations: TEXT, LEGEND • New routines: BARPLOT, ERRORPLOT • Changes to CONTOUR • COLORBAR • Changes to IMAGE • Changes to MAP • MAPGRID, MAPCONTINENTS • New Routines • VECTOR, STREAMLINE • Bugaboos with new routines

  4. So, what’s this new system, anyways? • Functional graphics • Old IDL direct graphics were procedural • Aspects of iPlot tools/object graphics systems • Scriptable • Dynamic Plot Changes without redrawing • Smart saving images • Old direct graphics system still works, so your code will still produce the plots • However, some things are worth merging over

  5. Graphics basis • No need to set device keywords • Opens new window with white background automatically • Stores graphical variables in memory, dynamically addressable • LaTeX-like syntax for special characters • Colors are stored in the system • Symbols are stored in the system • Can use text to specify symbols and colors (versus old specification of numbers) • Let’s start with just introducing the WINDOW W1 = window()

  6. Old code: Device, decomposed=0, retain=2 !p.background = 255 Loadct, 39, /silent Window, 0, xs=600, ys=600 Plot, findgen(10), color=0, /nodata oplot, findgen(10), color=250 New Code: P=plot(findgen(10), color=‘red’,$ dimensions=[600,600]) PLOT

  7. PLOT • Properties: • Under the old code, had to specify everything in one statement, e.g.: Plot, findgen(33)/16*!pi, sin(findgen(33)/16*!pi), color=0, xrange=[0,2*!pi], $ yrange=[-1,1], charsize=2.0, ystyle=1, xstyle=1 , $ ytitle=‘Y = sin(x), xtitle =‘ x = [0,2!7p!8]’,/nodata oplot, findgen(33)/16*!pi, sin(findgen(33)/16*!pi), color=250, thick=2 Oplot, findgen(33)/16*!pi, sin(findgen(33)/16*!pi), psym=3, color=0 • New code is dynamic – can set things separately as well as together P1=plot(findgen(33)/16*!pi, sin(findgen(33)/16*!pi)) P1.color=‘red’ P1.xrange=[0,2*!pi] P1.ytitle=‘Y = sin(x)’ P1.xtitle =‘x = [0, 2$\pi$] ;this is equivalent to: P1.symbol=‘plus’ P1.sym_color=‘black’ P1 = plot(findgen(33)/16*!pi, sin(findgen(33)/16*!pi), color=‘red’,$ xrange=[0,2*!pi, ytitle=‘y = sin(x)’, xtitle=‘x = [0, 2$\pi$],$ symbol=‘plus’

  8. Annotations • LEGEND: uses plot data to make legend, replacing old method of PLOTS and XYOUTS • TEXT: outputs text to screen (analogue: XYOUTS) • Create multiple plots with differing names • Use annotations.pro from collections

  9. BARPLOT • Draws a bar plot of data • Syntax: • B1 = BARPLOT(x, y) • Old syntax for bar plots in make_precip_barplot.pro • Let’s go to the code…

  10. ERRORPLOT • Specification: • E1 = ERRORPLOT(x,y,xerror,yerror) • Draws a box and whisker plot • All plot keywords the same • Find the code in make_precip_error.pro

  11. CONTOUR • Similar to other plotting systems, but with a twist! • Nonfilled contours similar to changes in PLOT system • Filled contours a little different… • Old code: Loadct, 39, /silent Max1 = max(data) Min1 = min(data) Contour, data, x, y, nlevels=251, /cell_fill, levels=findgen(251)/250.*(max1-min1) – min1, color=0 New code: C1 = contour(data,x,y,n_levels=251,/fill, rgb_table=39)

  12. COLORBAR • Remember how much of a pain making colorbars was? Not anymore! • Old code: Ncolors=255 Loc = [0.1,0.1,0.8,0.125] xsize= (loc(2) – loc(0))*D.X_VSIZE Ysize = (loc(3) – loc(1))*D.Y_VSIZE Xstart = loc(0)*D.X_VSIZE Ystart = loc(3) *D.Y_VSIZE Bar = BINDGEN(256)#REPLICATE(1B,10) Bar = BYTSCL(bar, top=ncolors-1) TV, CONGRID(bar, xsize, ysize), xstart+1, ystart=1 PLOT, findgen(251)/250., findgen(251)/250.*max1, /nodata, $ position=loc, yticks=1, ytickformat=‘(A1)’ yminor=1, xticklen=0.25,$ xrange=[min1,max1], xtitle=title1, color=0, /noerase, xstyle=1 • New code: Loc = [0.1,0.1,0.8,0.125] cbar1 = colorbar(target = c1, position = loc)

  13. CONTOUR and COLORBAR • Let’s go to the code… looking at the wind speed example • contour_windspeed.pro

  14. IMAGE • Replaces TV, does some other stuff as well… • Context: Im1 = image(bands, xval, yval, order=1) Old code: Tv, bands, xval, yval, order=1, true=3 -Still need order command to make things look right if you don’t rotate it -automatically senses if it’s a 3-band overlay (no more true=3) -Saves via im1.save, no more write_png, etc.

  15. MAP • Most overhauled routine • Moves it into more GIS/ENVI type mapping versus IDL direct mapping • Calling context: M1 = map(‘Equirectangular’, limit = [min(lat), min(lon), max(lat), max(lon)], position=[0.1,0.1,0.9,0.9], dimension=[900,900] Replaces: Map_set, limit = [min(lat), min(lon), max(lat), max(lon)], position = [0.1,0.1,0.9,0.9]

  16. MAP • The MAP command also leads to changes in MAPGRID and MAPCONTINENTS • Start a map… M1 = map(‘Geographic’, limit=[10,-130,50,-60], dimensions=[900,600]) Now, let’s change some properties… Mg1 = m1.mapgrid Mg1.linestyle = ‘Dash’ Mg1.label_position = ‘0’ Mg1.font_size=14 ;now, let’s add some continents Mc1 = mapcontinents(/countries) Mc1 = mapcontinents(/usa) ;now let’s change some properties! M1[‘Longitudes’].label_angle=0 M1[‘Ohio’].fill_color=‘red’ M1[‘Michigan’].fill_color=‘blue’

  17. MAP • The map works in projection space, not in the direct space anymore • So, let’s say we want to plot points in the map… of the NARR grid or something • Let’s go to plot_narr_latlon.pro

  18. VECTOR and STREAMLINE • Two new ways to plot wind features! • Some of these are pretty awesome! Context: V1 = vector(uwind, vwind, x, y, vector_style=‘barbs’) St1 = streamline(uwind, vwind, x, y, streamline_stepsize=0.1, streamline_nsteps=200) Let’s go to the code: start with stream_vector.pro

  19. Combination plots! • OK, so we have covered mapping, plotting, streamlines, vectors, colorbars… • Now let’s put some of these together in IDL 8.0 syntax. • Let’s look at combo_plot.pro and go from there…

  20. Bugaboos • Some issues that I haven’t figured out yet • More then these, just a brief synopsis • MAP • Inability to switch to decimal degrees • Haven’t quite figured out how to map a satellite image yet • Can’t specify position, automatically defined based on projection • Problems with multiple maps in the same window • CONTOUR • Filled contours have issue with fixed tables • Can be slow to save in EPS • COLORBAR • Can’t change range- specified in data • PLOT • Multiple axes can be slow if it’s not a direct multiplier • Skew-T in the new plotting system would be a nightmare

  21. Overview • IDL 8.0 makes simple things easier! • IDL 8.0 makes complex things harder! • Overall, adapt code as you see fit- I’m moving most of my new simple plotting (especially error and bar plots) to the new system, but will probably keep the old Direct Graphics for mapping and filled contours

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