Calculating maximum value

[Cylindric]

I'm trying to get two numerically-unrelated lines on one graph, to correlate a server's TPS with another metric. The problem is that one can be in the range 0-50k or even more, and the other is in the range of about 0-5.

To get these showing in a comparable way on one graph I've tried using CURRENT_DS_MAXIMUM_VALUE, but that seems to be the max value as defined in the DS, and not the max value currently "on screen", so I just get 'U'.

For some charts it works to use Logarithmic scaling, as that can visually expand the low items and still show the high items, but doesn't always look right, as the high-value line get's compressed.

Basically what I need is something like

a, MAX_VISIBLE_DS_VALUE, /, 100, *
and
b, MAX_VISIBLE_DS_VALUE, /, 100, *

Am I missing some obvious way of scaling a DS to 100%, when I don't know the actual max? In this example, TPS can be from 0 to 50k or even more, so the DS is setup as max "U".

[gandalf]

So, what exactly do you want to achieve? Do you want to change automatic scaling? Do you want to change y-axis to a percentage of something?
R.

[Cylindric]

I'm not sure how else to explain it. I can auto-scale the Y-axis already, Ideally I'd like to have a CDEF to scale a LINE1 to a range, but to do that I need to know the highest value in the current displayed date range.

For example, if you take only the left half of the data I attached above, I would
1. take the green values, divide by 30 and multiply by 100 to get a percentage
2. take the red values, divide by 5k and multiply by 100 to get a percentage
3. display them both on one graph.

But if you take only the right half of the data I would
1. take the green values, divide by 8 and multiply by 100 to get a percentage
2. take the red values, divide by 2k and multiply by 100 to get a percentage
3. display them both on one graph.


The bit of information I'm missing in my CDEF is the maximum value of a DS for a given date-range (the current graph).

Basically, I want to normalise two arbitrary DS so they can be compared. "Oh look, IIS connections is up, and so are SQL transactions/sec". I can't do that at the moment, because the green line dissapears if plotted on a 0-5k graph, and the red line flattens out if I use a log graph. Also, I can't arbitrarily "divide by 5k" for example, because the values vary so wildly.

[gandalf]

This looks like a VDEF approach (this may give you a max value of a ds) and, perhaps, a COMPUTE as well (to store computed data in an rrd file, using data of some ds' within that rrd but without dealing with CACTI ds naming conventions).
Both will be available with 089. You may have a try on current alpha code to verify
R.