Legends
leg_1.ncl: The resources in this
script contain the bare minimum to get a two item legend in the upper
left corner of the plot. The default values of many of these resources
draw a huge legend that is outside of the plot domain.
pmLegendDisplayMode = "Always"
Turns on the legend. The location of the legend within the plot is
controlled primarily by three resources. One chooses the reference
axis (pmLegendSide = "Top") and
the other two determine in NDC coordinates how far to move the legend
perpendicular (pmLegendOrthogonalPosF = -0.3 ) and
parallel (pmLegendParallelPosF =
.1) to this reference axis.
In this example the top axis is the
reference, and the Parallel value of .1 keeps the legend close to the
left axis. Increasing this value will move the legend at the same
"height" across the plot to the right.
Note that the orthogonal position is negative. This is expected. In this case decreasing values (e.g. from -0.3 to -0.4) would move the legend down the plot.
The default size of the legend is much to large for the plot, so
several resources are set to resize the legend:
pmLegendWidthF = 0.15
pmLegendHeightF = 0.18.
The default size of the legend labels is also too large, and so is scaled down with lgLabelFontHeightF = 0.03.
The values of the legend labels are determined by:
xyExplicitLegendLabels = (/"U","V"/). The default
value is the name of the variable.
Finally, the default box around the legend is turned off with:
lgPerimOn = False
leg_2.ncl: Adds a title and bounding box
to the plot. Changes the position of the legend.
lgTitleOn = True
lgTitleString = "Example"
lgTitleFontHeightF = .025, Turns on the title and
sets its value and font size.
leg_3.ncl: Demonstrates what
a legend looks like with colored markers. Swaps the orientation.
lgOrientation = "horizontal"
changes the orientation of the legend.
leg_4.ncl: In many cases there may be
very little space on a line plot to place a label, particularly when
there are many lines and the label is long. This examples demonstrates
making the legend horizontal, using the height and width attributes to
really shrink the lines, and then angling the labels in order to
shrink it even more.
lgLabelAngleF = 280., Changes the angle of the labels.
pmLegendWidthF = 0.12
pmLegendHeightF = 0.05
lgLabelFontHeightF = .02
were the values
I chose to make this legend small. You can experiment with values that
work for you.
leg_5.ncl: Demonstrates how to add a
common legend. There is no single gsn* resource to perform this
function because unlike a label bar, a legend can be placed anywhere
on the plot. Still, it is relatively easy to create. The resources
are the same, we just assign them differently.
A legend can have two types of labels. One is in the center of the line lgLineLabelStrings, and the other is at the end lgLabelStrings. This example uses the former, which is why several of the resources are different from the other legend examples.
leg_6.ncl: Demonstrates the addition
of a legend for a contour-on-contour plot.
gsn_legend_ndc is the function that will add a legend to a contour plot.
leg_8.ncl: Demonstrates how to create a
legend by using gsn_create_legend, available
in NCL version 4.2.0.a034. After the legend is created you have to attach
it to the plot by using gsn_add_annotation.
Note when using gsn_add_annotation that gsnDraw and gsnFrame must be set to False. This results in the need to call draw and frame after the legend is attached to the plot
leg_9.ncl: Demonstrates how to change
the order of the items in a legend using the lgItemOrder resource, added in version 5.0.1.