This code snippet is designed to identify and plot the last zigzag highs and lows on a price chart using the ProBuilder programming language. The zigzag pattern is a technical analysis tool used to filter out smaller price movements, making trends easier to spot.

zz = zigzagpoint[15]
lookback = 100

if islastbarupdate then
    //find last zigzag tops & bottoms
    a=0
    unset($zz)
    for i = lookback-1 downto 0
        itop = zz[i+1]>zz[i+2] and zz[i]zz[i+1]
        if itop then
            $zz[a]=zz[i+1]
            $zzbar[a]=barindex-(i+1)
            $zztype[a]=1
            lasttop = $zz[a]
            a=a+1
        endif
        if ibottom then
            $zz[a]=zz[i+1]
            $zzbar[a]=barindex-(i+1)
            $zztype[a]=-1
            lastbottom = $zz[a]
            a=a+1
        endif
    next

    //plot the zigzag tops & bottoms
    if a>0 then
        for i = 0 to a-1
            if $zztype[i]=1 then //is that a top?
                drawpoint($zzbar[i],$zz[i],3) coloured("cyan")
            else //nope! that's a bottom
                drawpoint($zzbar[i],$zz[i],3) coloured("crimson")
            endif
        next
endif

return lasttop, lastbottom

The code snippet above performs the following steps:

• Initialization: Sets the zigzag sensitivity and lookback period.
• Check for Last Bar Update: Ensures that the code executes only on the last update of the bar, optimizing performance.
• Identify Zigzag Tops and Bottoms: Iterates backwards through the price data to find points where a zigzag top or bottom occurs based on the defined conditions.
• Store Points: Stores the identified zigzag points, their corresponding bar indices, and whether they are tops or bottoms.
• Plot Points: Plots the identified points on the chart using different colors for tops and bottoms.
• Return Values: Returns the last identified top and bottom points for further use or analysis.

This code is useful for traders or analysts who want to visually identify significant price points and trends in financial markets using automated methods.