"Using Select with Loop Operator"

Hi Jegan,

you may use a macro for your loop operator. In the parameters tab you can enable "set iteration macro" and define a name for it. By default the macro value is incresed by one with every loop iteration. For the index in the select operator you specify %{macroname} and receive the highest index. Of course you may also specify the same value for the number of iterations in the loop and for the index. This can also be a macro, just have a look at "Set Macro" operator.

Cheers,
Helge

Here is an example process similar to what Helge described that may help if you are not familiar with the macros in loops and extracting macros:
In this case I aggregated on the label value to get the distinct number of values.  In your case you could replace this with month.

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<process version="6.0.008">
  <context>
    <input/>
    <output/>
    <macros/>
  </context>
  <operator activated="true" class="process" compatibility="6.0.008" expanded="true" name="Process">
    <process expanded="true">
      <operator activated="true" class="generate_data" compatibility="6.0.008" expanded="true" height="60" name="Generate Data" width="90" x="45" y="30">
        <parameter key="target_function" value="multi classification"/>
        <parameter key="number_of_attributes" value="2"/>
        <parameter key="attributes_lower_bound" value="0.0"/>
      </operator>
      <operator activated="true" class="aggregate" compatibility="6.0.008" expanded="true" height="76" name="Aggregate" width="90" x="179" y="30">
        <list key="aggregation_attributes"/>
        <parameter key="group_by_attributes" value="label"/>
      </operator>
      <operator activated="true" class="extract_macro" compatibility="6.0.008" expanded="true" height="60" name="Extract Macro" width="90" x="313" y="30">
        <parameter key="macro" value="NumExamples"/>
        <list key="additional_macros"/>
      </operator>
      <operator activated="true" class="loop" compatibility="6.0.008" expanded="true" height="76" name="Loop" width="90" x="179" y="120">
        <parameter key="set_iteration_macro" value="true"/>
        <parameter key="iterations" value="%{NumExamples}"/>
        <process expanded="true">
          <operator activated="true" class="generate_attributes" compatibility="6.0.008" expanded="true" height="76" name="Generate Attributes" width="90" x="246" y="30">
            <list key="function_descriptions">
              <parameter key="DummyAttribute_%{iteration}" value="%{iteration}"/>
            </list>
          </operator>
          <connect from_port="input 1" to_op="Generate Attributes" to_port="example set input"/>
          <connect from_op="Generate Attributes" from_port="example set output" to_port="output 1"/>
          <portSpacing port="source_input 1" spacing="0"/>
          <portSpacing port="source_input 2" spacing="0"/>
          <portSpacing port="sink_output 1" spacing="0"/>
          <portSpacing port="sink_output 2" spacing="0"/>
        </process>
      </operator>
      <operator activated="true" class="select" compatibility="6.0.008" expanded="true" height="60" name="Select" width="90" x="313" y="120">
        <parameter key="index" value="%{NumExamples}"/>
      </operator>
      <connect from_op="Generate Data" from_port="output" to_op="Aggregate" to_port="example set input"/>
      <connect from_op="Aggregate" from_port="example set output" to_op="Extract Macro" to_port="example set"/>
      <connect from_op="Aggregate" from_port="original" to_op="Loop" to_port="input 1"/>
      <connect from_op="Loop" from_port="output 1" to_op="Select" to_port="collection"/>
      <connect from_op="Select" from_port="selected" to_port="result 1"/>
      <portSpacing port="source_input 1" spacing="0"/>
      <portSpacing port="sink_result 1" spacing="0"/>
      <portSpacing port="sink_result 2" spacing="0"/>
    </process>
  </operator>
</process>

Thanks for your help: the above solution solved my issue