    Plot convergence in JDFTx output files using gnuplot. Usage:

            plotConvergence <file1> <file2> ...

    If multiple output files are specified, they will be plotted alongside.

    The behavior is controlled by several environment variables:
            nLines      Plot the final $nLines iterations (default: 1000)
            skipLines   Ignore the first $skipLines iterations (default: 0)
            iterType    Select iteration type: Elec (default), Ionic, Fluid etc.
            logTarget   Plot energy difference from $logTarget on a log axis.
            xAxis       "iter" (default) or "time" to plot versus iteration count or run time
            term        GNUPLOT terminal with options (default: GNUPLOT default with X, "dumb" without)
            out         GNUPLOT output file; match this with term (default None)