Hi Laura, It looks like PLOTSYM is from the AstroLib library which is a third party library. I have never used this library function before, so would it be possible to include a small example of what you are hoping to achieve? Apart from that the following example illustrates the use of a text annotation and the '$\Downarrow$' to create an arrow that points down. Alternatively you can also use '$\Upwnarrow$' for an upwards pointing arrow. This example comes from http://www.exelisvis.com/...xt_annotations.html. Hope this helps! ; Define the data. temp09 = [28,36,42,47,55,62,63,75,66,47,44,32] months = [1,2,3,4,5,6,7,8,9,10,11,12] ; Draw the first plot. p = PLOT(months, temp09, 'r', $ YTITLE='Temperature in $\circ$ Fahrenheit', $ XTITLE='Months', $ TITLE='Average Monthly Temperature', $ THICK=2) ; Add annotations to describe the data. arrow = TEXT(0.58, 0.64, '$\Downarrow$', /CURRENT) difftext = TEXT(0.5, 0.62, $ 'Greatest $\circ$ F $\Delta$', /CURRENT)

I guess my question could be restated as is there a way to plot user defined symbols in the plot function? Instead of a circle, 'o', square, triangle or any of the defined symbols I would like to use a user-defined symbol for plotting like PSYM does for the plot procedure. Is this possible in the plot function? ?? The way that PLOTSYM defines a down arrow is by the following: xarr = [0,0,.5,0,-.5]*psize yarr = [0,-2,-1.4,-2,-1.4]*psize fill = 0 Where psize is just a factor by which the symbol is multiplied/enlarged. I would like to use this user-defined symbol in my plotting which instead of putting a circle at a specific x and y on my plot, I would put this symbol where the base of the arrow begins at the data point.

I'm getting close to what I would like to plot and here is what I have: x=[3,1,8,3,5,10] y=[4,8,10,2,5,6] newplot=plot(x,y,symbol='_',sym_color='blue',linestyle=6,xrange=[0,11],yrange=[0,11],sym_thick=2) uppersym=symbol(x,y,sym_text='$\downarrow$', sym_color='blue', /data,sym_thick=2,sym_font_style=1,sym_size=1.5) However, I would like the base of the arrow to be at the horizontal line so that the line is point away from that data point. Any suggestions?

Laura, I would suggest including something like an offset for the y-values in the symbol call. Here is an example. Hope that answers your question! x=[3,1,8,3,5,10] y=[4,8,10,2,5,6] offset=.275 newplot=plot(x,y,symbol='_',sym_color='blue',$ linestyle=6,xrange=x_range,yrange=y_range,sym_thick=2) uppersym=symbol(x,y-offset,sym_text='$\downarrow$', sym_color='blue', $ /data,sym_thick=2,sym_font_style=1,sym_size=1.5)