summarize row values in a new column

KNIME Analytics Platform
1

As a newcomer to KNIME I do ask for help.

I want to sum up given numerical values of a column in a new column.

Example

iris-data  new_column

4.4           4.4
4.4            8.8

4.5          13.3

I can't find a standard node to sum up the values in iris-data.

		<p>I tried the column aggregator but without success.</p>
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2

You need the group by node.

It can be used for aggregations over all rows of a table grouping over the complete table. Hence, not using a group column.

In the second tab you can choose to get the sum over the iris-data column.

Cheers, Iris

3

Hi Iris,

I think that is not doing the expected thing. As I understood the original question was about running totals/partial sums. I agree that the GroupBy is closer to the answer than the column aggregation, but I think it is easier to solve with a Java snippet with something like:

double sum = 0;//should be among the fields
///...
sum += c_col;//You might want to check for missing, NaN or infinite values
out_column = sum;

Cheers, gabor

4

Actually there is a "Math formula" node in the "KNIME Math Expression (JEP)" extension which will do the job for you without need of any coding in Java.

5

Many thanks to everybody. Your comments are really helpful! I tried all your suggestions. Finally I used the 'Java Snippet' (simple) node, that worked out fine.

// Global Variable Declaration

Double sum = 0.0;

// Method Body

sum = sum + $iris-data$;  //$iris-data$ is the 'data column'

return sum;

 

I checked the radio-button 'append a new column' .

I checked the radio-button return data-type 'double'.

 

Best regards, Alfred

Many thanks to Rosaria Silipo at www.dataminingreporting.com/2/post/2013/04/cumulative-sums-in-knime.html