## Scaling waves for long ranges on log axis plots

jjweimer
Posts: 1325
Joined: 2007-08-14
Location: United States

I have just run in to a case where some clever trick may be needed.

I am trying to generate a theoretical curve that extends over nine orders of magnitude in x. Features of interest appear at 10^9, 10^13, and 10^16 in the scale. Using linear scales on the data waves, I loose resolution on features at the low end. I suspect that I have one of two options:

* Create an explicit x wave that is scaled logarithmically.
* Increase the number of data points in my scaled wave to recover the resolution at the lowest end.

Independently, I might wish for a new built-in feature to SetScale that would scale the x by logarithmic steps increments. Perhaps the x-scaling could even be designated by a function call (much as the TransformAxis package creates a new scaling axis).

```SetScale/F=ScaleFunction x, ...

Function ScaleFunction(p) : SetScale Function
variable p

return log(p)
end```

Is this idea worth any thought?

--
J. J. Weimer
Chemistry / Chemical & Materials Engineering, UAH

HJDrescher
Posts: 349
Joined: 2015-01-20
Location: Germany

Maybe you could remodel your function/wave to do the exponential/logarithmic part inside and use a linear x-scale (and of course adjust the label accordingly). As a drawback, the automatic tick features will probably fail, to my experience.

I'd support the request for log wave scaling. However, I'm aware that this will cause a lot of trouble 'below the surface'.

HJ

Posts: 1936
Joined: 2007-06-29
Location: United States

You probably have already figured this out:

```Make/N=(desiredPoints)/O/D xwave
SetScale/I x log(startx),log(endx),xwave
xwave = 10^x```

John Weeks
WaveMetrics, Inc.
support@wavemetrics.com

jjweimer
Posts: 1325
Joined: 2007-08-14
Location: United States

In the meantime, I do an equivalent to below for the three functions.

```Function calc_epdipole(ep0, tau, xx)
variable ep0, tau, xx

variable rtnv

rtnv = ep0/((xx^2*tau^2) + 1)

return rtnv
end

Function Update_Waves()

wave xe, eprd

variable ep0, tau, dep

variable ynD

// molecular (dipolar)
ControlInfo/W=Inputs check_d
ynD = v_value
ControlInfo/W=Inputs slider_ep0
ep0 = v_value
ControlInfo/W=Inputs slider_tau
tau = 10^(v_value)

eprd = ynD*calc_epdipole(ep0, tau, xe[p])

...
end```

The graph shows eprd vs xe (and others). I generated xe as `xe = 10^(8 + p*(2e-4))` over 45001 points.

The inherent ability to set the scale on waves by a function would be cool.

--
J. J. Weimer
Chemistry / Chemical & Materials Engineering, UAH

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[ last edited April 9, 2018 - 15:35 ]