How to match x of two functions f(x) and g(x) in order to plot f as a function of g


It is certainly simple but I don't know how to do it. 

I have an excel sheet with 4 coulumns: x1, f(x1), x2, g(x2) 

x1 and x2 represents the same physical parameter but the incremental step is different, as for example:

x1             x2

0                   0

0.504             0.486

1.001               0.653

1.526             1.026

2.312                1.486 

My question is how to find the rows where x1 match x2 with 1% of percentage of error in the sheet and delete all the other rows. So I can plot f as a function of g after that. I put my excel sheet in the attachment.  

Thank you for your help,


Hello ChakibO,

With 1% of percentage of error do you mean that you want to consider a 1% range of each value both for x1 and x2?

Thank you,



Couldn't you do it like this, assuming you have two separate KNIME tables x1, f(x1) and x2, g(x2):

For each of the two tables:

  • Use a Math Formula node to add a column to each table that rounds the x value to your chosen precision - e.g. ROUND($x1$, 2)
  • Use a GroupBy node to group on the rounded x value column and aggregate the f(x) or g(x) column - use the mean, or whatever aggregation makes most sense. The output from this node is a table with two columns, the rounded x value and the corresponding aggregated f(x) or g(x) value.

Now you can pass the two tables from the GroupBys into a Joiner node set to Inner Join on the two rounded x columns. The output will contain rounded x, f(x) and g(x).

Thank you Tom,

Indeed It works,