EXTERNAL

SUB spctrm (p(), m, k, ovrlap, w1(), w2())

    LIBRARY "four1"

    DECLARE FUNCTION input$       ! Defined in the driver

    FUNCTION window (j)

        LET window = 1 - abs(((j - 1) - facm) * facp)
        ! LET window = 1
        ! LET window = 1 - (((j - 1) * facm) * facp)^2

    END FUNCTION

    LET mm = m + m
    LET m4 = mm + mm
    LET m44 = m4 + 4
    LET m43 = m4 + 3
    LET den = 0
    LET facm = m - .5
    LET facp = 1 / (m + .5)
    LET sumw = 0
    FOR j = 1 to mm
        LET sumw = sumw + window(j)^2
    NEXT j
    FOR j = 1 to m
        LET p(j) = 0
    NEXT j
    IF ovrlap=-1 then
       FOR j = 1 to m
           LET w2(j) = val(input$(12, 1))
           IF mod(j, 4) = 0 then LET dum$ = input$(2, 1)
       NEXT j
    END IF

    LET jn = 0
    FOR kk = 1 to k
        FOR joff = -1 to 0
            IF ovrlap=-1 then
               FOR j = 1 to m
                   LET w1(joff + j + j) = w2(j)
               NEXT j
               FOR j = 1 to m
                   LET w2(j) = val(input$(12, 1))
                   IF mod(j, 4) = 0 then LET dum$ = input$(2, 1)
               NEXT j
               LET joffn = joff + mm
               FOR j = 1 to m
                   LET w1(joffn + j + j) = w2(j)
               NEXT j
            ELSE
               FOR j = joff + 2 to m4 step 2
                   LET w1(j) = val(input$(12, 1))
                   LET jn = jn + 1
                   IF mod(jn, 4) = 0 then LET dum$ = input$(2, 1)
               NEXT j
            END IF
        NEXT joff

        FOR j = 1 to mm
            LET j2 = j + j
            LET w = window(j)
            LET w1(j2) = w1(j2) * w
            LET w1(j2 - 1) = w1(j2 - 1) * w
        NEXT j

        CALL four1 (w1(), mm, 1)

        LET p(1) = p(1) + w1(1)^2 + w1(2)^2
        FOR j = 2 to m
            LET j2 = j + j
            LET p(j) = p(j) + w1(j2)^2 + w1(j2 - 1)^2 + w1(m44 - j2)^2
            LET p(j) = p(j) + w1(m43 - j2)^2
        NEXT j
        LET den = den + sumw
    NEXT kk
    LET den = m4 * den
    FOR j = 1 to m
        LET p(j) = p(j) / den
    NEXT j

END SUB