[slang-users] Using the csv module

[Morten Bo Johansen <mbj@xxxxxxxxxxx>]

Hi

I am dabbling a little with the csv module. I would like to
create a few functions whereby I can calculate my daily intake
of various nutrients from a csv data file and print out how
these align to the official recommendations. I suspect the
results from my diet will be appalling, but that's another
matter ;)

Of course, I need to be able get the data from the intersecting
cells of rows and columns. The lines (very curtailed) of the
data file look like this in an English version:

  ,,,Waste,"Energy, kJ","Energy, kcal",Nitrogen-to-protein factor,"Nitrogen, total" ...
  Number,Group,Name,%,kJ,kcal,-,g,g,g,g,g ...
  1,Soft fruit,"Strawberry, raw",4,162,38,6.25,0.106 ...
  2,Pome fruit,"Apple, raw, all varieties",10,233,55,6.25,0.043 ...
  3,Tropical or subtropical fruit,"Banana, raw",41,396,93,6.25,0.183 ...
  4,Root and tuber vegetables,"Potato, raw",25,326,77,6.25,0.324 ...

So if I do:

  variable csv_file = "food_data.csv";
  variable csv = csv_decoder_new (csv_file);
  variable datastruct = csv.readcol ();
  variable colstruct = csv_readcol (csv_file; has_header);

then I can get all the food items with

  variable food_items = datastruct.col3;
	
and all the nutritional items with	

  variable nutr_items = get_struct_field_names (colstruct); % [""], lower case

finding row and column numbers for particular items with e.g.

  variable N = where (nutr_items == "energy, kj")[0];
  variable F = where (food_items == "Strawberry, raw")[0];

But how do I access the intersecting cell of N and F to get the value, 162?
I don't understand csv.readrow. It seems that you can't read a particular
numbered row with it? If I use it on this example, it just returns NULL.
It also returns NULL with the example from csvfuns.hlp.

In this example, the "energy kj" values would be in datastruct.col5 and so I
could get the value, 162, with datastruct.col5[F], but this is not the way,
I suppose.

Thanks,
Morten

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