5 Replies Latest reply on Feb 24, 2014 3:14 PM by Darren.Metcalfe

# PI Processbook

Hi

I've created a PDI which basically shows weekly spend on energy at numerous buildings on one of my companies sites. Using performance equations I've created a coloumn which displays the difference in spend between the previous week and the week previous to that (hope that makes sense). What I'd like to do is add  to the display an arrow which displays if the weekly spend has increased or decreased (green arrow up for decrease in spend, red arrow down for increase in spend).

I can obviously add the arrow but I'm unsure how to develop the method of how the arrow changes when spend increases / decreases. I'm a bit of a newbie so apologies if this a bit vague. I've read through the process book manual but struggling to find anything which points towards this.

• ###### Re: PI Processbook

Hi Darren

A simple method I've used before would be to create a Performance Equation returning 0, 1 or 2 (or possibly -1, 0 or 1) according to the three outcomes of this. If it's a weekly number only to be compared to last weeks number, you can just use simple PE functionality to compare this week's number to PrevVal(...).

In ProcessBook you'd use a multi state functionality on three graphical symbols. I've found it best to use symbols without a black border, and then place the three so that they overlap. The multi state will have to be set up so that the color is transparent (none) when it's out of state, and a good color when the state matches your arrow. I used a green arrow pointing upwards for a positive number, a yellow arrow pointing straight forward for the 0 number (same as last week), and a red arrow pointing downwards for a negative number.

If you need a more advanced calculation on determining the slope of a trend, you'll be looking at calculating the derivative for the trend. I think there's a function in PE called Arma, but I haven't used it.

• ###### Re: PI Processbook

Hello,

Arma actually calculates dynamic response for Auto Regressive Moving average model, which is very useful for process control engineers.

@Darren: I don’t see any function to calculate the derivative but you can apply its definition for discrete time series, and it will work great.

• ###### Re: PI Processbook

Hi Asle

Thanks very much for your help, I'm looking into your method and using the knowledge. Could I just ask, did you use symbols from the symbol library or add your own symbol? The reason I ask is the the symbols within the symbol library all have black borders and if I add my own symbol, I'm unable to add a multi state function to it as the option is not available.

Many Thanks

• ###### Re: PI Processbook

I had to look this one up, I see the date on the PDI file is 2009 so it's a bit long time ago :)

Under the symbol library ASHRAE Ducts, the first symbol is a simple, black arrow called 'Duct air flow direction'. Using this you'd be able to accomplish what you want.

(I see I've used the Arrange -> Rotate command to rotate the upwards/downwards arrows indicating this week's value has changed)