openHAB - negative value transformation

Setup, Configuration and Use Beginners
1
  • Platform information:
    • Hardware: Laptop
    • OS: Windows 11
    • openHAB version: 3.4.3
  • Issue of the topic: getting negative value from PV-installation - would like to convert it to positive value before showing on a label

I am retrieving the power generation of my PV-installation. So far so good. I am getting (absolutely logical) negative values. Again, so far so good. Now I would like to change this value into a positive value before showing it on a label.

I am a openHAB newbie - old but still willing to learn.

I searched the internet for hours, and also this community - but didn`t find a solution which I understand or beeing able to implement.

I hoped that there is a solution which can be easily implemented while working in the UI-mode - without a need to create extra files nor programing.

Any help would be very much appreciated.

Regards
Mausepaul

2

Do you mean only change the value for display or actually change the state of the item?

Also, display where? Autogenerated widgets, custom widgets, sitemaps?

3

I mean only change the value for display - no state change is planed.

I would like to create a widget just for showing this value on my overview page. it is currently running fine - just showing the (correct) negative value. Just for my “convenience” I would like to show the value as positive value.

4

root square of the square…

5

Andreas,

thanks for your valuable reply… Or was it just to show me my (already known) stupidity.

Yes I am old, yes I am an absolute beginner - but I am still willing to learn.

So, any help is very much appreciated.

Cheers

6

The widget expressions have access to the javascript Math object so you can use Math.abs

label: =Math.abs(@@'nameOfItem')
7

Justin,

thanks a lot for your reply.

Tried it - but (maybe wrongfully done) it doesn’t work:

image
image1102Ă—700 27.3 KB

8

Right, sorry. I forgot to convert the item state string to a number. That adds one more level of difficulty. To convert you have to use parseInt (or parseFloat):

label: =Math.abs(Number.parseInt(@@'Things_OpenWB_OpenWB_Pro_PV_Power_Generation'))

But the problem there is that will strip off the unit. So you can either manually add the unit back on:

label: =Math.abs(Number.parseInt(@@'Things_OpenWB_OpenWB_Pro_PV_Power_Generation')) + ' W'

or (my recommendation) just cheat and manipulate the string instead of doing actual math:

label: =(@@'Things_OpenWB_OpenWB_Pro_PV_Power_Generation').replace('-','')
1 Like
9

Justin,

THANKS A LOT for your effort in helping me out!

I’ll give it a try (currently no more power from PV…) - but your solution looks great for me.

This will be a next step ahead.

Really appreciate your help!

Mausepaul