data from picure to graph

[paul_s]

is there a simple way to use data from say the draw circle by radius vi and plot it on an xy graph? I want to be able to highlight my latest data point with a circle or something (seperate plot)

[djadjok]

Maybe it will be simplier to just add another plot to XY graph consisting of only one datapoint (the last one) and with different (enlaged) point style?

[paul_s]

i'm already using the largest points... I really need to make it stand out from the others. It's on a psychometric chart as background (white with lots of grids), and most points are plotted to quite a small area of the chart. I'll just draw it from a for loop i suppose. Does anyone know the maximum # points XY graph can plot? Excel2000 is 32000. Or does it just depend on system used?

[djadjok]

Hmm... For me it seems that changing form/size/color will be sufficient to distingue one point from the others usually, but you can also overlay your graph with a transparent picture control and do some drawing there (but this will require for sure some additional coordinate transformations).
I don't know exact data on limitations on the maximum number of points in LV (if any) - may be someone other can answer you.

[paul_s]

psycho? I think i meant psychro...
thanks defuflo. I think an overlay would be a little too much for this. I just want to put a box around it.

[Underflow]

How about something like the attached (in LV6.0.2)? It finds the last point, then calculates and generates a circle of other points around it.

A bit simplistic, but it was fun to make 🙂

[paul_s]

Thanks Underflow, that's pretty much exactly what I did actually... except I was using lines instead of points and therefore needed a lot more iterations to get a decent circle. Good Idea! The only mistake you made was not putting the circle on top of the other points 🙂 (My data is very crowded)

[Greg_McKaskle2]

> Thanks Underflow, that's pretty much exactly what I did actually...
> except I was using lines instead of points and therefore needed a lot
> more iterations to get a decent circle. Good Idea! The only mistake
> you made was not putting the circle on top of the other points 🙂 (My
> data is very crowded)

Sounds like you may already have a solution, but if not, use trig
functions to sample as many points on the circle as you feel that you
need. 100 points will probably be good for a circle of radius of
diameter 30 pixels.

You asked how many points you can plot in a LV XY plot. The answer is
that the hard limit at the moment is 2 billion. Practically, you can't
plot that many because you will run out of memory first. With unlimited

memory, I'd guess you could plot 500 million byte sized integers without
a problem. Other datatypes take more memory and thus would run into the
memory limit sooner. People routinely plot millions of points coming
from DAQ cards.

Greg McKaskle

[Jim_Kring]

Paul,

You take a look at complex numbers as a solution for drawing stuff in x-y space. They�re perfect because LabVIEW has built-in functions for converting between Cartesian and polar coordinates. Essentially, complex numbers are LabVIEW-native 2D vectors with a few nice mathematical operations. I've adapted Underflow's example to show you what I mean.

Cheers,

-Jim