NCL > Application examples > Basic examples
Basic example 2
How to set the size and location of a plot; how to draw multiple plots on a single frame
This is an introductory example that shows how to specify viewport settings to adjust the size and location of a plot and how to position multiple plots on a single frame. This example demonstrates how to create the plot using NCL, HLU C, and HLU FORTRAN library calls. The names of the example codes that create this plot are basic02n.ncl, basic02c.c, and basic02f.f.
Discussion
This module discusses how to size and position an NCAR Graphics plot using HLU C library calls, HLU FORTRAN library calls, and the NCAR Command Language. The example produces two frames that are drawn into an X Window.The first frame of the example shows how to set the viewport (an object's bounding box) for an object using the vpXF, vpYF, vpWidthF, and vpHeightF resources. vpXF and vpYF are resources that specify the location of the left and top edge, respectively, of a viewport window. The values are specified in Normalized Device Coordinates (NDCs), such that the lower-left corner of the frame corresponds to the coordinate point (0,0), and the upper-right corner corresponds to the coordinate point (1,1). The vpWidthF and vpHeightF resources specify the width and height, respectively, of the viewport. These values are also specified in NDCs.
The second frame of the example shows how to draw multiple plots in a single frame. This is accomplished by drawing the first object, then resetting the viewport to specify a different plot location and size, then drawing the object again. These steps can be repeated multiple times to draw multiple plots on a single frame.
This example does not use any data and is therefore more useful for instruction rather than for creating useful graphical output. A detailed discussion about how to create the plot appears in the comments of the source code for the example.
Creating the plot using HLU C library calls
The HLU C program that generates this plot is called basic02c.c.
Creating the plot using HLU FORTRAN library calls
The HLU FORTRAN program that generates this plot is called basic02f.f.
Creating the plot using NCL
The HLU NCL program that generates this plot is called basic02n.ncl.
The data
No data is used in this plot.
How to run this example
There are three ways to produce this example: by using an NCL script (basic02n.ncl), a C program (basic02c.c), or a FORTRAN program (basic02f.f). The examples are installed in the following locations:
- $NCARG_ROOT/lib/ncarg/nclex/basic/basic02n.ncl
- $NCARG_ROOT/lib/ncarg/hluex/basic/basic02c.c
- $NCARG_ROOT/lib/ncarg/hluex/basic/basic02f.f