When multiplying one vector by another, we see a vectorised operation occurring. But what happens when, we've run out of elements to consider. For example, if I was to use a flip flop vector of two, of length two. This doesn't really make sense mathematically. 

Whereas, where if I wrote this out by pen and paper, each vector would have to have the same length and here, we have a length of six and in the flip flip vector, we have a length of two. Yet in R, this does make sense. Why does the above multiplication make sense? The two elements of flip flop are reused or recycled when multiplying by prices. That is to say, we take the first pair, six and five and then we repeat with the second pair, three and four. And then we repeat again with the final pair, two and a one. The small vector is repeated to the needed length of the larger vector. 

To explain what's going on behind the scenes, let's consider the length of prices, let's consider the length of flip flip, let's consider the division of the larger one by the smaller one and what we needed to repeat, in order to ensure that flip flop became the same length as prices. Now behind the scenes of our initial multiplication of our two vectors, this is what's going on behind the scenes. Where does vector recycling fail? If, for example, the longer object was not a multiple of the shorter object length. For example, if I was to try prices multiplied by this vector of four, we'd return a warning on the screen.