I need to make a line chart with the month on horizontal axis and a value on the vertical axis.
I need to colour the line's segments in green if the trend based on the previous month is growing, or in red if the trend is decreasing.
I can't find a way to compare the values grouped by month, and I prefer not to perform this by adding another query from db.
Right-click on the Chart Series (the line of the graph) and select Series Properties...
, click Fill
on the left then click the fx
button to enter and expression for the fill. Let's say your field is called Sales. Use the following expression for the Fill:
=IIF(Fields!Sales.Value >= Previous(Fields!Sales.Value), "Green", "Red")
This worked on my simple test. You may need to aggregate within your query (group by month and sum) for this to work properly.