Graphing problem with two plots

[Tom]

I know how to plot two graphs on top of one another but the problem I have
is as follows. I have the spectrum of a certain noisy signal which has been
averaged. I then change some conditions by pressing a button and the
spectrum changes to something else. of course I can capture both of these
graphically but really I want them both on the same graph - any ideas?
The data is not available at the same time - would I have to store it
somewhere in a buffer and recall it in some way? Picture a spectrum analyser
where there are two channels - you take the spectrum on channel A and then
store it. You then take the spectrum on channel B and do a comparison where
they appear together - this is my problem in essence.

thanks


tom

[Bill Choy]

You can use a shift register in while loop to act as a buffer to feedback the signal. When you press a button, keep the original data on the register and use merge signal to plot your new signal with the old signal on the same graph. Hope this help.

Bill

[altenbach]

If both writes to the graph occur in the same loop ( just at different iterations), use shift registers. (See attached simple LabVIEW 7.0 example).

If the writes occur in different parts of the diagram, Just write the first channel to a local variable of the graph, then later combine the two channels for the final graph.

[Tom]

"Bill Choy" wrote in message
news:5065000000050000003B940100-1079395200000@exchange.ni.com...
> You can use a shift register in while loop to act as a buffer to
> feedback the signal. When you press a button, keep the original data
> on the register and use merge signal to plot your new signal with the
> old signal on the same graph. Hope this help.
>
> Bill
Thanks Bill - tried this and it failed as the array sizes were different ie
the Buffer compared with the new spectrum. They could not be bundled
together for plotting.

Tom

[Bill Choy]

Hi Tom,

Take a look of altenbach example. This is a very good one to solve your problem.

Bill