2D plot with units question

On 2/19/2010 4:42:58 PM, Mona Zeftel wrote:

>In Mathcad Prime 1.0, you can
>have units on plots, so the
>question arose
>about showing units on the
>markers. We want to show them
>but what if two
>or more traces have different
>unit scaling? This would be a
>conflict if
>you have a marker where two or
>more traces intersect.

I think we need to back up a bit here and establish what it is one actually plots on a graph. The ONLY thing you can plot on a graph is a number. You cannot plot, for example, 5 tonnes as a point. That is why the quantity must always be divided by an appropriate unit before plotting. I can plot 5*tonnes/tonnes, which shows as a value of 5, or 5*tonnes/kg, which shows as a value of 5000, but I can't plot 5*tonnes or 5000*kg. Incidentally, that's why the strictly correct way of labeling an axis is quantity/units, not quantity (units), and you should allow people to use this form of labeling.

>What is the point below for a
>marker, 4.9? 4.9 kg or 4.9 m?

The point is at 4.9. Like anything else on a graph, a point can only have purely numerical coordinates. Your apparent conflict occurs because, as Tom has already pointed out, you are asking a nonsensical question to begin with. You might as well ask "how many 1kg masses do I need to make a 3 meter length?". I understand what you want, but the reason you will never be able to come up with a satisfactory way to do it is because there is no way to do it.

Richard

For some reason I can't see any of the images in your message.

I'm trying to decide why I would want to see units in a marker on a plot? I would typically want to see the units in the title (whether I type it myself or PRIME inserts it) so I don't necessarily need to see it on a marker.

Could be I'm missing part of the story without seeing your examples.

Preston

If two traces have different units they cannot (logically) intersect. An intersection of the actual lines is meaningless.
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