calculate difference between two columns using tMap

[Cherichoc-]

One extraction is from Json and the other from an existing table. I want to great a variable in tmap that will be added In the output
JSON                                          ExistingTable                     OutputVar
Latitude                                        latitude                                latitude
-24.50                                          -24.10                                   0.40

Then if the variable difference is greater than 0.50 use the JSON data. I can use the tFilter row for that

[Anonymous]

The problem you have here is linking the two datasets. Do you have a key that can join them?

[Cherichoc-]

They are joined by deviceID with both longitude and latitude

tExtractJasonField>>>>tMap<<<<<<tDBinput

                                          |

                                          | 

I need to create variable that will calculate the [existing coordinates(from tdbinput) minus new coordinates(from jSon)]

[Anonymous]

Then join the data using the tMap and subtract one from the other.

[Cherichoc-]

row1.latitude - row2.latitude is not working

[Anonymous]

What is the data type of your GPS columns? I suspect that they might be Strings. They need to be Doubles

[Cherichoc-]

datatype is double

[Anonymous]

Subtraction should work then. Can you show the tMap you are trying this in? I'll need to see the whole screen so that I can see data types and the expressions that are used