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ClosestDate ( TestDate ; ValueList )

Find the closest date between a one to many relationship.

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Ken Newell Hamilton Glaucoma Center

  Function definition: (Copy & paste into FileMaker's Edit Custom Function window)

/* ================================================== 03/12/2005 1.0 KLN Original Version ================================================== PURPOSE: To find the closest date in a table to a date in a related table. This is accomplished by capturing the related dates to a value list for parsing out. ================================================== USER INPUTS TestDate = The Date field in the Current Table To Find Closest To ValueList = Name of the Value List That Contains Related Dates VAIRABLES gList = Value List Dates To Be Checked gClosestDate = Closest Test Date gNum = Number Of Related Dates As Determined From Value List OTHER CUSTOM FUNCTIONS USED ClosestTestSub which is recurvise checking all dates. ================================================== */ Let ([ gList = ValueListItems ( Get ( FileName ) ; ValueLIstName ); gClosestDate = MiddleValues ( gList ; 1 ; 1 ); gNum = If ( IsEmpty ( glist ) ; 0 ; PatternCount ( gList ; "¶" ) + 1 ) ];ClosestTestSub ( TestDate; gList; gClosestDate; gNum ) ) The second is a subfunction which is recursive and is: /* ================================================== 03/12/2005 1.0 KLN Original Version ================================================== PURPOSE: To find the closest date in a table to a date in a related table. This is accomplished by capturing the related dates to a value list for parsing out. ================================================== INPUTS (Provided By The Calling Function) TestDate = The Date field in the Current Table To Find Closest To gList = Value List Dates To Be Checked gClosestDate = Closest Test Date gNum = Number Of Related Dates As Determined From Value List OTHER CUSTOM FUNCTIONS USED ClosestTest which sets up the vairables for this sub-function. ================================================== */ If ( gNum > 0 ; ClosestTestSub ( TestDate; gList; If ( Abs ( TestDate - gClosestDate ) > Abs ( TestDate - GetAsDate ( MiddleValues ( gList ; gNum ; 1 ) ) ) ; GetAsDate ( MiddleValues ( gList ; gNum ; 1 ) ) ; gClosestDate ); gNum-1 ) ; gClosestDate ) Click to copy

This function is really 2 custom functions. The first sets up the variables and calls the sub function whcih is recursive and input of the value list is intended to be a related value list.

To help show what the function does imagine the following setup:

Table A has a date, a relationship is created to Table B which also has a date. Going from Table A to Table B is a one to many relationship.

The first parameter is the date in table A in which you are trying to find the closest date in table B related records. A vlaue list of the related dates from Table B is created and the name of this list is the second paramenter passed in the function.

Lest say the Date in Table A is 3/13/2005. The related dates are 1/1/2005, 1/15/2005, 3/1/2005, 3/14/2005. The function returns the date of 3/14/2005 as it the closest test date to 3/13/2005. In this case we have defined the closest date to be able to be either before or after the date being tested.

By modifying the subfunction compare statement the logic could be changed to force the closest test to have to be before . Using the same example above the function would return 3/1/2005. This function could be call PriorTest.

In addition it could be altered so the closest test would have to occur after the test date.

If someone wanted they could add an additional parameter that could control the behavior; but since that was not what I needed I ended here.

Any way if you do modify it by adding to I would love to here about it and get a copy. Thanks and enjoy.

 

Comments

		Shawn Rowland, Webconsort LLC Aug 14, 2019
Need a little help here. I think I am missing something where is ClosestTestSub function?

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