# Compare payload value to last received payload
**URL:** https://discourse.nodered.org/t/compare-payload-value-to-last-received-payload/48351
**Category:** General
**Created:** [13 July 2021 08:59 UTC](https://discourse.nodered.org/t/compare-payload-value-to-last-received-payload/48351 "2021-07-13T08:59:53Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@JoshuaG](https://discourse.nodered.org/u/JoshuaG)
#### Post date: [13 July 2021 08:59 UTC](https://discourse.nodered.org/t/compare-payload-value-to-last-received-payload/48351/1 "2021-07-13T08:59:53Z")
I receive a payload value that rises every second, after a while it'll stop for a moment and reset to 0 again.
What I want to do is capture that max value.
I'm struggling to hold onto the last value to compare it against the new one.
---
### Author:  [@zenofmud](https://discourse.nodered.org/u/zenofmud)
#### Post date: [13 July 2021 09:19 UTC](https://discourse.nodered.org/t/compare-payload-value-to-last-received-payload/48351/2 "2021-07-13T09:19:10Z")
You will need to save the last value. You could use a `function` node to save the value as a node variable and check it each time a msg comes thru or you could use a `switch` node and a `change` node to test and save (if the new value is greater) the value as a flow variable.
If you haven't worked with context, take a read of the documentation here: [Working with context : Node-RED](https://nodered.org/docs/user-guide/context)
---
### Author:  [@dceejay](https://discourse.nodered.org/u/dceejay)
#### Post date: [13 July 2021 09:30 UTC](https://discourse.nodered.org/t/compare-payload-value-to-last-received-payload/48351/3 "2021-07-13T09:30:55Z")
You can also look at the smooth node - as that also can return the max value seen (as well as mean, min, etc) - and can be reset by a msg.reset message.
---
### Author:  [@JoshuaG](https://discourse.nodered.org/u/JoshuaG)
#### Post date: [13 July 2021 10:04 UTC](https://discourse.nodered.org/t/compare-payload-value-to-last-received-payload/48351/4 "2021-07-13T10:04:33Z")
Solution:
```auto
pl = msg.payload.CycleTimeMach;
pl2 = msg.payload.CycleTimeMan;
avg = flow.get("AvgOldMach.S8")
avg2 = flow.get("AvgOldMan.S8")
if (pl < avg) {
flow.set("AvgNewMach", {S8: avg})
}
if (pl2 < avg2) {
flow.set("AvgNewMan", {S8: avg})
}
flow.set("AvgOldMach", {S8: pl})
flow.set("AvgOldMan", {S8: pl2})
```
I was trying to do it with the flow context last night but my head just wouldn't compute. I guess all I really needed was a good coffee and fresh eyes.
Edit:
Probably worth adding that I setup the context in another node using
```auto
flow.set("AvgOldMach", {S8: 0})
flow.set("AvgNewMach", {S8: 0})
flow.set("AvgOldMan", {S8: 0})
flow.set("AvgNewMan", {S8: 0})
```
from a one-hit timestamp injection that fires every time the flow starts
---
### Author:  [@zenofmud](https://discourse.nodered.org/u/zenofmud)
#### Post date: [13 July 2021 10:24 UTC](https://discourse.nodered.org/t/compare-payload-value-to-last-received-payload/48351/5 "2021-07-13T10:24:56Z")
> [@JoshuaG](#):
>
> Probably worth adding that I setup the context in another node using
>
> ```auto
> flow.set("AvgOldMach", {S8: 0})
> flow.set("AvgNewMach", {S8: 0})
>
> flow.set("AvgOldMan", {S8: 0})
> flow.set("AvgNewMan", {S8: 0})
>
> ```
>
> from a one-hit timestamp injection that fires every time the flow starts
In the `function` node you could use this
```auto
avg = flow.get("AvgOldMach.S8") || 0 // get flow var, it it doesn't exist use 0
avg2 = flow.get("AvgOldMan.S8") || 0 // get flow var, it it doesn't exist use 0
```
and eliminate the need to have the other node to set up the context.
---
### Author:  [@JoshuaG](https://discourse.nodered.org/u/JoshuaG)
#### Post date: [13 July 2021 10:56 UTC](https://discourse.nodered.org/t/compare-payload-value-to-last-received-payload/48351/6 "2021-07-13T10:56:40Z")
Ah brilliant, I couldn't figure out how to achieve this.
thanks
---
### Author:  [@zenofmud](https://discourse.nodered.org/u/zenofmud)
#### Post date: [13 July 2021 11:00 UTC](https://discourse.nodered.org/t/compare-payload-value-to-last-received-payload/48351/7 "2021-07-13T11:00:26Z")
The users guide is very informative: [Writing Functions : Node-RED](https://nodered.org/docs/user-guide/writing-functions#storing-data)
---
### Author:  [@system](https://discourse.nodered.org/u/system)
#### Post date: [27 July 2021 11:01 UTC](https://discourse.nodered.org/t/compare-payload-value-to-last-received-payload/48351/8 "2021-07-27T11:01:00Z")
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