Expression: Find Lowest Non-Zero Number?

Ignition
1

Hello, I have a set of tags with values, [0,2,0,1].

I need to find the lowest non-zero number from my set in expression language. The min() expression always brings back the zeros.

Any ideas? Thank you.

2

Hmm… not that it’s any use to you now, but maybe a filter expression function that operates on lists would be a good idea…

3

Anyway you probably have to do this in script and if you really need the resulting value in an expression for some reason invoke that function via runScript.

4

Thanks Kevin,

I think I’ve figured it out…

min(
if({[.]tag1}=0,999,{[.]tag1}),
if({[.]tag2}=0,999,{[.]tag2}),
if({[.]tag3}=0,999,{[.]tag3}),
if({[.]tag4}=0,999,{[.]tag4}),
999)

5

Ah, there you go :slight_smile:

Maybe another cup of coffee will make me smarter.

2 Likes
6 
min(
	max({[.]tag1}, 999),
	max({[.]tag2}, 999),
	max({[.]tag3}, 999),
	max({[.]tag4}, 999),
	999
)

Same effect, less duplicate tag paths (thus less chance for future errors in transcription).

1 Like
7

Actually, I think that would stomp on the other numbers non zero numbers? anything < 999 would always be 999.

4 Likes
8

Using the given [0,2,0,1]
this

becomes

min(
	max(0, 999),
	max(1, 999),
	max(0, 999),
	max(2, 999),
	999
)

which becomes

min(999,999,999,999,999)

I wish I was a little more fresh with my math because I feel like this could be done strictly using min/maxes, buts right now its not coming to mind. Doing it in an expression is a little tough, you will definitely need if statements. This might be one of those times where a runScript() is appropriate and do your calculation via scripting.

9 
min(
	if({Tag1}, {Tag1}, None),
	if({Tag2}, {Tag2}, None),
	if({Tag3}, {Tag3}, None),
	if({Tag4}, {Tag4}, None)
)
10

Lord, these are all ugly. I would definitely use objectScript(), like so:

objectScript("min([999]+[x for x in args if x])", {tag1}, {tag2}, {tag3}, {tag4})

{ Using my free Simulation Aids module, naturally. }

4 Likes
11

Just noting a lot of these solutions, for a set of [1, -2, -3, -4] would return -4, not 1 - you definitely just want a Non-Zero min, so every other number positive and negative is fair game? Or you want the minimum of non-negative values?

Clarifying because getting a lowest non-negative number is a very common case, but getting a minimum by excluding one specific number from the entire number line, does not seem as common.

12

Positive values, presumably, as zero is explicitly excluded. My solution becomes:

objectScript("min([999]+[x for x in args if x>0])", {tag1}, {tag2}, {tag3}, {tag4})
2 Likes
13

In my case, yes, non-negative non-zero #'s, also in my use case there won’t ever be negatives.

1 Like