This is so basic I'm embarassed to ask. I don't understand Y0 and dY?

[abarkan]

After using LabVIEW for 4 years, I'm so embarassed to admit I don't get Y0 and dY (and X0, dX). Just now, I was trying to make the y-axis on my chart read from -0.01 to 0.1 in 0.01 steps (so -0.01, 0, 0.01, 0.02, 0.03, ... 0.1). But I can't!?!? It seems to me that I should make Y0 = -0.01 and dY = 0.01, but this doesn't work. I've tried numerous things, and I've played this game numerous times in the past, but always I had to give up. How can this trivial task be so elusive?
abarkan@imra.com

[Jim_Kring]

Try using the Range property instead of Scaling (Xo and dX). The range defines what data is shown in the graph, while you are "changing" or scaling the data by using the Xo and dX propeties.

-Jim

[Mikael_Garcia]

Abarkan,
Yes, this is a very confusing part in LabVIEW. As Jim said in his answer, Yo and dY are for scaling and that is something different.

To set the scale on the Y-axis you have to create a property/attribute node for the XY graph.

In LabVIEW 6, the parameters you need to set can be found in the property node under:

/Y scale info/ Y Range/

Do not forget to set the property node to All write first since the default is All Read.

In older versions of LabVIEW, you find the parameters in the attribute node under:

/Y scale/Range/

However, this is not the end of the story. It can still be tricky to get the plot to look like you want. The reason for that is that:

1. You need to make the plot area big enough to get your increment size on the axis.

2. You ne
ed to have a precision that will allow your increment size.

Change those two settings and you will see that your Y-axis changes.

Attached is a simple VI that shows how to set your Y-axis. It is compatible with LabVIEW 4.1 and up.

Hope this helps.

/Mikael Garcia

[AIR]

Hi,

The problem might be, that the precision of the x-scale is default 1
(e.g. -0.01 gets 0.0). Put it to 2 (e.g. -0.01 stays -0.01). Then it works
fine.

Regards,

Wiebe.


"abarkan" wrote in message
news:506500000008000000F4280000-993342863000@exchange.ni.com...
> After using LabVIEW for 4 years, I'm so embarassed to admit I don't
> get Y0 and dY (and X0, dX). Just now, I was trying to make the y-axis
> on my chart read from -0.01 to 0.1 in 0.01 steps (so -0.01, 0, 0.01,
> 0.02, 0.03, ... 0.1). But I can't!?!? It seems to me that I should
> make Y0 = -0.01 and dY = 0.01, but this doesn't work. I've tried
> numerous things, and I've played this game numerous times in the past,
> but always I had to give up. How can this trivial task be so elusive?
> abarkan@
imra.com

[Brent_R]

Abarkan,

The Y0 and dY settings in the Y Scale Formating dialog are used for scaling and shifting the display of your data, not for setting the display range and increment on the axis. Y0 applies an offset to the data. For example, if Y0 is set to 0.50, then a value of 1.00 is displayed as 1.50. Likewise, dY applies a scaling factor to the displayed data. If dY is set to 2.00 (and Y0 = 0), then a value of 1.00 is displayed as 2.00. For most applications, these values should be set to Y0 = 0 and dY = 1. Please see Mikael's response for good description of using property nodes (formerly attribute nodes) to control the appearance of the Y-axis.

Best Regards,

Brent Runnels
Applications Engineer
National Instrumetns