The purple line is an extension of the trend line of the fork: from the pivot point to origin of the 100% limit of the fork (here, the low yellow line). Andrews called it the “Hagopin line” and considered it very important for the interpretation of the movement of the price after it leaves the fork, since it can represent a moving and pre-established magnet. In this construction, it is related to the “mini median line” which is a small fork based on closing points in a limited time frame. Andrews liked this mini-fork very much and thought that it could give an early signal for a change in trend, as discussed in my previous post.
P.S. : Notice that, so far, the 100% yellow line was a a reasonable support for SPX…
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