This Excel LAMBDA function calculates the coordinates for two series to add to a scatterplot to produce a vertical and horizontal line

excel-lambda-chartQuadrants.txt

chart.Quadrants = LAMBDA(seriesData,
    LET(
        // The first column (x values)
        x, TAKE(seriesData, , 1),
        // The second column (y values)
        y, TAKE(seriesData, , -1),

        xMax, MAX(x),
        yMax, MAX(y),

        // Assuming we want lines as close to the "middle" as possible
        xMid, INT(xMax / 2),
        yMid, INT(yMax / 2),

        // To make the use of HSTACK shorter - that's all!
        H, LAMBDA(one, two, HSTACK(one, two)),

        // Create the coordinates of the beginning and end of each line
        H(
            {"Vertical Line"; ""; "Horizontal Line"; ""},
            VSTACK(H(xMid, 0), H(xMid, yMax), H(0, yMid), H(xMax, yMid))
        )
    )
)