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interpolate missing data between points

  1. #1
    Rocket Rod
    Guest

    interpolate missing data between points

    Is there a way to automatically interpolate missing data between data points
    in a spreadsheet
    eg there might be a list of sequentail dates and a value against each one
    but there might be 4 values missing.
    By selecting the cells before and after teh missing 4, and choose a funtion
    of interpolate, it automatically determines theer are 4 missing, theerfore
    divides teh difference by 5 and adds that to each of the cells in turn -
    filling in teh blanks.

    Perhaps could be enhanced with options of moving average to calculate teh
    next point

  2. #2
    Jerry W. Lewis
    Guest

    Re: interpolate missing data between points

    Linear interpolation or other? If other, then more information is needed.

    If the known data is contiguous, with the points to be interpolated
    elsewhere on the sheet, you could use the FORECAST() function for linear
    interpolation. If you want actual and interpolated data all together in
    one array, then you will have to program the formula manually.

    For linear interpolation, this is not difficult. For concreteness,
    suppose dates are in column A with values in column B, and that B2 is to
    be interpolated for A2 from A1:B1 and A3:B3. You can linearly
    interpolate with
    =B1+(A2-A1)*(B3-B1)/(A3-A1)
    in B2. Copy/paste the formula into other cells with missing values,
    (provided that you don't have 2 missing values in a row).

    Jerry

    Rocket Rod wrote:

    > Is there a way to automatically interpolate missing data between data points
    > in a spreadsheet
    > eg there might be a list of sequentail dates and a value against each one
    > but there might be 4 values missing.
    > By selecting the cells before and after teh missing 4, and choose a funtion
    > of interpolate, it automatically determines theer are 4 missing, theerfore
    > divides teh difference by 5 and adds that to each of the cells in turn -
    > filling in teh blanks.
    >
    > Perhaps could be enhanced with options of moving average to calculate teh
    > next point



  3. #3
    BobT
    Guest

    Re: interpolate missing data between points

    Follow-up to Jerry:
    if you are missing more than two values in a row, say from
    B2 to B6,
    B2> =B1+(A2-A1)*(B$7-B1)/(A$7-A1)
    copied down will fill in all the values.
    If there is a way to find the next row down in the column
    that is not a formula you could do away with the absolute
    reference that has to changed in every new section of
    missing data.

    for example instead of B$7 use indirect("B"&row(B2)+match
    ({NotFind("=")Formula},B3:B$65536,0)
    (While avoiding a circular ref)

    Is there a way to find the first entry in a range that is
    a value, not a formula?

    >-----Original Message-----
    >Linear interpolation or other? If other, then more

    information is needed.
    >
    >If the known data is contiguous, with the points to be

    interpolated
    >elsewhere on the sheet, you could use the FORECAST()

    function for linear
    >interpolation. If you want actual and interpolated data

    all together in
    >one array, then you will have to program the formula

    manually.
    >
    >For linear interpolation, this is not difficult. For

    concreteness,
    >suppose dates are in column A with values in column B,

    and that B2 is to
    >be interpolated for A2 from A1:B1 and A3:B3. You can

    linearly
    >interpolate with
    > =B1+(A2-A1)*(B3-B1)/(A3-A1)
    >in B2. Copy/paste the formula into other cells with

    missing values,
    >(provided that you don't have 2 missing values in a row).
    >
    >Jerry
    >
    >Rocket Rod wrote:
    >
    >> Is there a way to automatically interpolate missing

    data between data points
    >> in a spreadsheet
    >> eg there might be a list of sequentail dates and a

    value against each one
    >> but there might be 4 values missing.
    >> By selecting the cells before and after teh missing 4,

    and choose a funtion
    >> of interpolate, it automatically determines theer are 4

    missing, theerfore
    >> divides teh difference by 5 and adds that to each of

    the cells in turn -
    >> filling in teh blanks.
    >>
    >> Perhaps could be enhanced with options of moving

    average to calculate teh
    >> next point

    >
    >.
    >


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