Addding Data with DIFFERENT Scales

[ahramos]

I've got two sets of data that I need to do some basic math with. One is set at 5 min intervals while the other is set at 6 min intervals. Is there some way to do this without manually manipulating one set of data?

 

[IRstuff]

The general approach would be to run a spline fit on one set of data and interpolate to get matching time scales

TTFN

FAQ731-376

 

[ahramos]

Thanks IRstuff for your response. I thought about your suggestion before, but it doesn't work out so well. I've monitored supply and return water temps from a chilled water loop as well as the flow. I need to apply the following formula for each data point to calculate tons cooling: Tons = gpm x dT / 24.

Basically I need a value for gpm, CHWS temp and CHWR temp to align at the same time. The overall average is easily calculated but is not as helpful as the overall trend of cooling tons over the period measured.

I've also tried using the VLOOKUP function of the dates in a numerical format. I even tried ROUNDING the values to one, two and three decimal points but couldn't make it happen. (Not sure if that's explained clearly but I could forward a portion of the data to anyone out there.)

 

[IRstuff]

I don't understand what you think you've tried. The only way to align the data is through interpolation. You can use either linear or spline.

TTFN

FAQ731-376

 

[handleman]

How about just pasting some of it here?

 

[joerd]

I agree with IRstuff, you'll have to interpolate. I would think that the data you have for gpm should be pretty constant, so you could almost take the average over the time period, unless you have a step change, then you would take two or more separate time periods.

Cheers,
Joerd

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[bacon4life]

This problem sounds just like what I working at a couple of weeks ago.

IRstuff, do you have specific plugin or macro you would suggest using to do a spline fit? Google found a bunch for me, but I am a bit hesitant to run randomly downloaded macros.

Thanks

 

[IRstuff]

I do most of my stuff in Mathcad, but ExcelCalcs is supposedly pretty reasonable:

http://www.excelcalcs.com/component/option,com_remository/Itemid,36/func,fileinfo/id,207/

TTFN

FAQ731-376