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Programmatically set y-axis in VIVA in Log Scale

Paolo Minotti

Hi there,

I want to plot the input referred noise of an instance.


I enter in the Calculator / ADE Outputs

getData("in" ?result "noise")


By default, y-axis, that is expressed in V/rt(Hz), is in linear scale. It would be much more interesting and intuitive to have it visualized in log scale.

Of course, one can right-click on the y-axis label, and select "Log Scale".

Is there a way to to this programmatically?

In particular, I would like not to use any SKILL function, I would like to just change the expression in the Calculator / ADE Outputs.

Thank you!

Paolo

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  • Andrew Beckett

    Paolo,

    If  you did a log sweep in the noise analysis, it should get plotted with a log x-axis automatically, and so what I'm suggesting below wouldn't be necessary (it gets the xScale hint on the waveform from how it was swept in the simulator - with spectre, anyway).

    Otherwise you can override the hint that's stored on the waveform object by using an expression like this:

    let(((in getData("in" ?result "noise"))) in~>xScale='log in)

    Yes, it's a piece of SKILL code, but you can put this in your output expressions or use it as part of another expression. What it's doing is getting the original result and storing it in a temporary variable, setting the xScale attribute on the waveform object, and then returning the waveform object.

    Regards,

    Andrew.

  • Paolo Minotti
    Dear Andrew,
    thank you for your reply.

    Actually, the axis I want to be displayed in log scale is y-axis (not x).
    I tried to adapt your solution, using
    let(((in getData("in" ?result "noise"))) in~>yScale='log in)
    but it does not work, i still have input-referred noise PSD plotted in linear scale.

    Paolo
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  • Andrew Beckett

    Hi Paolo,

    My apologies - I misread your question. Also, the way I suggested is not the best anyway - better to use the underlying vector objects (as this method works for both X and Y axes; there is limited support for the hint on the waveform object itself):

    let(((in getData("in" ?result "noise"))) drGetWaveformYVec(in)~>scale="log" in)

    Regards,

    Andrew.

  • Paolo Minotti
    Dear Andrew,
    this solution works perfectly.
    I really appreciate your help.

    Best regards,
    Paolo
    --
  • danco
    in reply to Andrew Beckett

    Hi Andrew,

    Is there a way to send the output to a secondary Y axis in a similar manner?

    Regards,

    Dan

  • Andrew Beckett
    in reply to danco

    Dan,

    If the y-axes have different units then they will automatically plot on different axes (so if ~>units on the y vector is different).

    Or if plotting from SKILL/OCEAN functions, you could use the ?yNumber argument. For example:

    plot(VT("/OUTP") VT("/OUTM") ?yNumber list(1 2))

    Regards,

    Andrew.

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