Retrieving data from a table

[foxxrunning]

I want to fill in a calculated field in one record using the value of a field in another record. How do I access a particular field in a particular record from within a function call? Thanks for any help as I have been unable to figure out how to do this.

[Stan Mathews]

Re: Retrieving data from a table

How is the particular record related to the target record?

[foxxrunning]

Re: Retrieving data from a table

If I understand what you mean by "related", each record is in the same table, one above the other.

[Stan Mathews]

Re: Retrieving data from a table

Then what you mean is you want some value in the previous record applied to the current record.

See the Previous() function.

Also see http://wiki.alphasoftware.com/Default+Values

[foxxrunning]

Re: Retrieving data from a table

I probably didn't pose the question with as much accuracy as I might have, so I will try again in the words of my partner Aaron. He wrote to me:
I was afraid he would say that because we only asked for how to get data form the previous record as opposed to getting data from any other record.
We might try asking how to make a function that compares my weight this year with my weight 10 years ago. So, the table I am working with has one record
for each year for past 50 years and each record has a field, WEIGHT, that has my weight for that year. It has a calculated field, WEIGHT_CHANGE, that I want
to be filled in by WEIGHT[y] - WEIGHT[y-10]when y is greater than 10. When y is 10 or less, WEIGHT_CHANGE[y] is 0. Going a step further, I would like to
have a function weight_change(d) that give WEIGHT[y] - WEIGHT[y-d]. This might be done by treating the table as an array of by using their table functions
like FETCH to retrieve values in other records directly.

I hope this description is able to clear up what we are trying to do. Again, thanks for any help.

[Al Buchholz]

Re: Retrieving data from a table

I probably didn't pose the question with as much accuracy as I might have, so I will try again in the words of my partner Aaron. He wrote to me:
I was afraid he would say that because we only asked for how to get data form the previous record as opposed to getting data from any other record.
We might try asking how to make a function that compares my weight this year with my weight 10 years ago. So, the table I am working with has one record
for each year for past 50 years and each record has a field, WEIGHT, that has my weight for that year. It has a calculated field, WEIGHT_CHANGE, that I want
to be filled in by WEIGHT[y] - WEIGHT[y-10]when y is greater than 10. When y is 10 or less, WEIGHT_CHANGE[y] is 0. Going a step further, I would like to
have a function weight_change(d) that give WEIGHT[y] - WEIGHT[y-d]. This might be done by treating the table as an array of by using their table functions
like FETCH to retrieve values in other records directly.

I hope this description is able to clear up what we are trying to do. Again, thanks for any help.

In pseudo code
1. Define an index based on the person and year
2. read the first record using a fetch_find based on the person and the starting year
3. store the values needed in variables (weight)
4. calculate the next value to look at in a variable - person and year-day passed into the function as an argument
5. read that record using fetch_find with the variable from step 4
6. calculate with the variables from step 2 and the values you just read in step 4

[foxxrunning]

Re: Retrieving data from a table

Al Thank you for your help. We will try this when next we get together.

[Mike Wilson]

Re: Retrieving data from a table

David,
I thought this a fun exercise so I worked up an example for you using a little different strategy than Al's. I didn't understand what the "d" represented when you wrote WEIGHT[y] - WEIGHT[y-d] so it's likely I didn't address that. There is a small explanation on the opening form of the example.

[foxxrunning]

Re: Retrieving data from a table

Mike,
Thank you so much for your effort. It will take us a few days to go through the complete work you created. I am truly grateful for your help.