Re: plotting irregular press axis at regular intervals

From: Mary Haley (haley AT
Date: Mon Oct 10 2005 - 20:57:11 MDT

  • Next message: Dennis Shea: "Re: canonical correlation"

    Hi everybody,

    There have been a flurry of internal email messages on this topic, and
    I thought I'd post what I hope is the answer to Duane's question. I
    don't have Duane's full script, so I've attached a sample NCL script
    that does what I think he is trying to accomplish.

    Please note that Duane is not using "gsn" calls, but rather
    object-oriented NCL code, so the attached code may look completely
    different to what some of you are used to seeing.

    As a side, if one *is* using gsn calls and wants to linearize an
    irregular axis, then the way to do this is by setting the
    gsnYAxisIrregular2Linear (or gsnXAxisIrregular2Linear) resource to
    True. For an example of using this resource, please see the first
    example at:

    Now, back to Duane's object-oriented code: just setting trYAxisType to
    "LinearAxis" is not going to work here, because that just effectively
    makes the tickmarks on the Y axis linear, but it doesn't actually
    transform the data along with it. In order to force the data through a
    transformation, you need to overlay the contour plot on what we call a
    "LogLin" plot. A "LogLin" plot is nothing more than something that
    defines a linear or logarithmic transformation for the data being
    overlaid on it.

    The attached script creates and draws a contour plot with an irregular
    Y axis. It then overlays this plot on a LogLin plot to linearize the Y
    axis, and redraws the plot so you can see the transformation.

    Note that this overlay business is effectively what happens behind the
    scenes when you set the gsnYAxisIrregular2Linear to True and use
    the gsn* functions.

    BTW, the attached script was taken from the following example, if you
    want to see more detail:


    On Mon, 10 Oct 2005 wrote:

    > Hi all,
    > My apologies for the 2nd email but in my response below to Duane I meant
    > to say:
    > trYAxisType=LinearAxis
    > and not
    > trYAxisType=LogAxis
    > Adam
    >> Hi Duane,
    >> If I understand your question correctly, you would like to change the
    >> Y-axis type from logarithmic to linear. Try setting the resource
    >> trYAxisType=LogAxis
    >> If that doesn't work or if I misunderstand your question let us know.
    >> Adam
    >>> I have pressure-lat diagrams that have an irregular pressure gridding
    >>> e.g., 1000, 900, 700, 300, 200, 100, 50, 10
    >>> but would like to plot it such that the vertical pressure axis looks
    >>> "regular"
    >>> eg. equal spaced 100 mb increments.
    >>> I've looked over many examples and still can't find one that does
    >>> this but presume it is something that can be done.
    >>> Thanks
    >>> Duane
    >>> Duane E. Waliser
    >>> Jet Propulsion Laboratory, MS 183-505
    >>> California Institute of Technology
    >>> 4800 Oak Grove Drive, Pasadena, CA 91109
    >>> 818-393-4094 (tel); 818 354 0966 (fax)
    >>> _______________________________________________
    >>> ncl-talk mailing list
    >> _______________________________________________
    >> ncl-talk mailing list
    > _______________________________________________
    > ncl-talk mailing list

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