Using Interactive Plot Functions

This topic describes some basic steps for using ENVI Classic plot windows. See Spectral Profile for the recommended method of working with plot windows in ENVI.

For more information on using ENVI Classic plot windows, refer to the "Plot Functions" tutorial in the ENVI Classic Help. Windows users can access the help by clicking the Start menu and selecting Programs > ENVI x.x > ENVI Classic Help. Linux users can access the help by typing envihelp -classic from a terminal window.

The following options are available in an ENVI Classic Plot Window when you right-click:

Plot Key: Enable or disable plot key labels.

Stack Plots: Offset all plots within the window so there are no overlapping data plots.

Set Stack Offset: Set the amount of offset between each stacked plot. Enter the value in percent data range.

Auto Scale Y-Axis: Rescale the y-axis to the data minimum and maximum when adding or updating plots.

Reset Range: Reset the x and y plot axes to their default data ranges or minimum and maximum values.

Clear Plot:Clear the plot data.

File: Select input and output formats.

  • Input formats include ASCII and ENVI spectral library.
  • Output formats include ASCII, ENVI spectral library, IDL variable, PostScript file, or image file.

Edit: Set Data Parameters, Plot Parameters, and x/y plot Data Values. Data parameters control the line types, colors, and other attributes of plotted data. Plot parameters control the axes, titles, and data ranges plotted.

Plot_Function: Opens a dialog to allow you to edit the following plot functions:

  • To plot the band number (or other index number) on the x axis, select Plot_Function > X Axis:Index.
  • For plots of images with wavelengths in the image header, plot the wavelength on the x axis, select Plot_Function > X Axis:Wavelength.
  • For plots of images with wavelengths in the image header, plot the wave number (1/wavelength) on the x axis, select Plot_Function > X Axis:1/Wavelength.
  • To replot the data displayed in the window with its continuum removed, select Plot_Function > Continuum Removed. The continuum is the convex hull that fits over the data and is divided into the original data values to produce the continuum removed values. The continuum is calculated using the first and last data points displayed in the plot, so for plots that have been zoomed, the continuum is calculated based on the displayed data range only.
  • To re-plot the data displayed in the plot window as binary encoded plots (0s and 1s), select Plot_Function > Binary Encoding. Binary encoding replots the data as a spectrum of 0s and 1s. It calculates the mean of the data and encodes each value as a 0 if it is less than or equal to the mean and as a 1 if it is greater than the mean.
  • To re-plot the original data values, select Plot_Function > Normal.