i have a workflow . ı want to use pie chart . but i created pie chart , it doesnt show anything.
it is difficult to try to help with such little information. Could you share your workflow (File --> Export KNIME Workflow) so we can have a closer look?
Once you have a data table in your workflow, you can pass it to the Reporting Tool with the Data to Report node. This makes the data available within the Report Designer so you can create a Pie Chart directly from there. Once you create your Pie Chart (or any chart) the first step is to bind it to your data from the workflow. This can be done directly from the chart creation wizard or later on. You can then fully customize your pie chart. If you omit to bind the data to the chart, an empty chart will be displayed. This may be your problem.
As an alternative, you can create a pie chart directly inside your KNIME workflow and then pass on to the Reporting Tool just an image of it (like a screen-shot) using the Image to Report tool.
Hope this helps, but if you could share a copy of your problematic workflow then I will be able to be more precise about what is possibly wrong with it.