Sign in to follow this  

Evaluate syntax

Recommended Posts



I am having a problem with the syntax of evaluate

I can get this expression to work

evaluate(Sites[Site_ID[0]] + "_Pressure1_Current[0]") /10  - where Sites[Site_ID[0]] =NB

I can this expression to work

evaluate(max(NB_Pressure1_Current[0,1000]))/10 - I know I don't need evaluate for this expression but for syntax testing I needed to confirm it works

but I cannot get this expression to work

evaluate(max(Sites[Site_ID[0]] + "_Pressure1_Current[0,1000]"))/10

I'm trying to Substitute "NB" in expression 2 with Sites[Site_ID[0]] from expression 1 so it will work with multiple sites

after a few hours of trying I'm not having much luck in getting the syntax correct.....

your help appreciated!!





Share this post

Link to post
Share on other sites

That's because max() returns a number not a string and evaluate expects a string.  You either want the max outside the evaluate, or inside a string, so either:



evaluate("max(" + sites[...)


Share this post

Link to post
Share on other sites

thanks got that to work

I have another related syntax issue

I have a button with a set to as the action

if I use exp1 below it works and updates the channel

however I need the expression to be dynamic and update based on what site it is

exp2 does give me the desired string in the result but when I use that expression it won't update the channel

I tried Exp3 but I think that actually evaluates the expression - it does not return the string needed to update the channel

I think I'm close but I just cannot figure out what syntax the expression needs to be






Share this post

Link to post
Share on other sites

The Set To action can only take a channel or variable.  Think of it like the left side of an assignment:

myChannel = 5

You can't do:

sin(myChannel) = 5

and Evaluate() is a function just like sin().

To do what you want, you'll have to use a Quick Sequence and execute.  Something like:

private string datain = system.entryDialog("Enter a value:")
if (!isempty(datain))
   execute(sites[site_ID[0]] + "_Tank_Install_Height[0] = datain")



Share this post

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this