field pointer question

[eeetee]

hi again:

i have a table that contains sanding truck information. the driver may use 1 of 4 types of material (sand/salt/mix1/mix2) and may select an application rate for this material (1 of 9). these rates are set by the administration in the truck and stored in the trucks table for lookup. below is the (abbreviated) table field structure.

Sand_1 c 3
Sand_2 c 3
Sand_3 c 3
...
Sand_9 c 3
Salt_1 c 3
Salt_2 c 3
...
Salt_9 c 3
Mix1_1 c3



etc etc etc

i have the material type (1,2,3 or 4) and the switch position 1..9. what i need to do is to point at the field in the table using these pointers. if sand 1 is the first field and i have mix1 at an application rate 5 selected by the driver i would weight the subtract 1 from the material type (3-1=2) multiply that by 10 (for the number of fields in a material type) and add the application rate switch setting to point at the field containing the actual rate setting.

3-1=2
2*10=20
20+5=25
i need to point at the 25th field in the record to get the correct rate. any suggestions on how to do this?
etc

thanks again!!

ed

[Tom Cone Jr]

RE: field pointer question

Ah hah! Another spreadsheet guy appears!

Ed, why not simplify your structure? Use two fields: Material and Rate.

The material field could hold values representing , sand, salt, mix1, mix2

the Rate field could hold the value representing the rate at which the material is applied.

When you do the calc just use the same two fields each time. You'll get distinctive results each time because the two fields will vary from record to record.

Otherwise, don't you have to parse through all the possible combinations of material and rate just to find those which aren't empty, before beginning your calc? This is necessary in a spreadsheet, but it's not needed at all in databases.

-- tom

[eeetee]

RE: field pointer question

hi tom:

thanks for your reply!

nope, not a spreadsheet guy, just not explaining what i wanted to do very well.

my client has about 200 sanding trucks, each one can be set to use one of the 4 material types. the truck uploads data into a5 in a compressed format. within the truck data there are two fields indicating material type (1..4) and a rate switch position (1..9). the rate switch may or may not have the same application setting from truck to truck (ie. truck1 rate_1 could be 1000kg/km and truck2 rate_1 could be 800kg/km). to further complicate things there are differences between material types within (ie. sand rate_1 could be 800kg/km and salt rate_1 could be 200kg/km). there are a 36 fields in each truck record to hold the values that the truck was set for (4 materials at 9 rates/ea). i was incorrect above with the math it should have been multiply by 9 instead of 10. the way the truck sends it's data for example material mix1 fills in the material field = 3 and rate switch fills in the rate field 5 (if it is set at 5). this is the only data that is avaiable from the truck. that is why i have to do a "lookup" not by record number but look at one specific field in a record depending on the combination of material type and rate switch setting.
i'm currently pondering creating a set with the truck fleet number as the parent and the application rates as a child. it would just save having to re-design a bunch of stuff that works well now.

thanks again tom!!

ed

[Tom Cone Jr]

RE: field pointer question

From the interactive editor:

tbl = table.open("names.dbf")

fild = tbl.field_get(2)

?fild.value_get()
= "Tom Cone "

tbl.close()


In this case the second field in the table structure was the 'name' field, and the value of that field was "Tom Cone "

Maybe something like this would work for your situation.

-- tom

[eeetee]

RE: field pointer question

hi tom:

thank you!!! i can't believe that is that simple!!

ed