Change a value in a message object

General
1

Hi

I have the following function as part of my weather station dashboard-

var m = {
"series": ["Rainfall"],
"data":[msg.payload[0] ["sum(RAINFALL)"]],
"labels":["Todays Rainfall"]
};
return {payload:[m]};

Long story short the data is rainfall sum from my database and is in inches. I've been running it this way for 3 years. I wish now to modify it to mm (*25.4) before returning the message to my chart. Could somebody please explain how I can do this inside of this function.

This is how the data appears when returned:

[{"series":["Rainfall"],"data":[0.293],"labels":["Todays Rainfall"]}]

Thanks
Derek

2 
var m = {
  "series": ["Rainfall"],
  "data": [msg.payload[0]["sum(RAINFALL)"] * 25.4],
  "labels": ["Todays Rainfall"]
};
return {payload:[m]};
3

Thanks Steve. I gave up trying to put it in the right place!

Thanks for your help.
Derek