.. meta:: :description: Basic calculator usage :keywords: calculator, magnitude, square root .. _calculator-uv-speed: Apply a calculator to convert u and v into speed ------------------------------------------------- .. note:: This document is part of a series teaching how to :ref:`create-image-sea-surface-speeds` Here we assume you alred :ref:`loaded 2D ocean data` Now we want to apply a "Calculator" filter to compute the absolute speed from the velocity. Choose Filters->Common->Calculator, or use the calculator symbol just above the pipeline. .. image:: 04-pipeline.png In the calculator, you can chose the data type to operate on ("cell data" is correct here), give your result variable a sensible name -- we chose ``vel`` here -- ``speed`` would have been correct... Naming your output immediately is useful, as color maps are associated with these names, so "Result" can lead to conflicts and hassle once you have a second calculator. In the next field, you can define the equation that is computed. We want to use:: sqrt (u*u+v*v) You can also use the drop-down menus at the bottom to get access to the variables available (sorted by scalars and vector quantities). .. image:: 05-calculator.png The result should look similar to this: .. image:: 05a-speed-image.png With the speed computed, you can :ref:`chose-BuGn` Alternatively, you can :ref:`rescale-colormap-to-custom`