# How do I use findvalue /RMD for x-value

I have an xy wave, say y is height and x is time. How do I use the findvalue  /RMD to find the height at a given time?

I assume that by xy wave you mean a 2D wave containing both height and time values (otherwise there is no need for /RMD).

You would use findvalue/RMD to search the dimension (row or column) of the 2D wave that contains the time data, then take the height from the corresponding row/column.

Yes, a 2D wave. What would be the syntax of /RMD ?

I've tried a number of combinations and am not finding value.  Also used /T = deltaX

for example

`tolerance =deltaX(myLineFitdata)`
`findvalue /V=(searchTime) /RMD=[0,*][0,*] /T=(tolerance)  myLineFitdata`

if column 0 contains time and column 1 height, then something like

`FindValue /V=(searchTime)/RMD=[][0,0] myLineFitdata`

I still can't get it to work  - here is my code and debugger details

searchTime =  myHEEventStartTime[k] -  myRVDZTimeDifference[k]
findvalue /V=(searchTime) /RMD=[][0,0]  myLineFitdata
myoutput[k] = myLineFitdata(V_row)

searchTime = 3724010668.16396 (Variable)

I skipped the /T flag in my post, but you probably need to reinsert that.

make /N=(5,2) foo = p + 2*(q==1)
findvalue /RMD=[][0]/V=(4) foo
print v_value
4
print foo[v_value][1]
6

Looks like your screenshot is a 1D fit wave, not a 2D wave. Then you simply use the wave scaling:

print LineFit_Lat(searchTime)

Note the curved parentheses.

The automatically generated output from curve fitting is waveform. Execute:

`DisplayHelpTopic "The Waveform Model of Data"`

so x-values are computed rather than stored.

Igor interpolates linearly, but has no way of knowing how to extrapolate.

Mike- you have done so much with Igor that is so sophisticated, that I hesitate to suggest it... The confusion over wave scaling, waveform data vs multidimensional vs XY data suggests that you may benefit from a quick review of the Getting Started help. I find that every few years even I benefit from reviewing Getting Started, and I wrote a lot of what's in there!

> may benefit from a quick review of the Getting Started help.

On every level of IP expertise consulting the documentation is required. I consult the documentation really often as well.

I do as well and my insomnia is now a thing of the past.

More seriously, I do browse it to get a better understanding of what can be done when the need arises.

Andy