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Execute this statement by clicking on the step icon !Step Icon.png|thumbnail,border=1,height=50! in icon  Image Added in the Editor. This should bring up the Figure 1 window. Note that the green arrow moves to the next statement indicating that execution is paused there.
Click again on the step icon. clf will clear anything in the current figure i.e. figure 1. This means you start with a clean slate.

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