Regular expressions help with HTML source code

I'm looking to parse through some HTML source code to pull information from the Wall Street Journal. I need to pull the price of the following commodities: the 4 domestic crude oil spot prices, copper, aluminum, cotton, and cocoa

This is the URL: http://online.wsj.com/mdc/public/page/2_3023-cashprices.html

I'm having some trouble with getting regexp to work the way I want it to.

what string expression would you use to pull out the middle (bold) price listed? If the value is n.a., it's okay if it just returns 'n.a.' or its equivalent.

I tried a variety of methods and I couldn't get it to work.

Could someone show an example of the string he or she would use for extracting the price?

Thanks!

Answer 1

[Cedric Wannaz]

Did you see my answer to your previous question? Tokens work well in such situations;

 >> buffer = urlread('http://online.wsj.com/mdc/public/page/2_3023-cashprices.html');

 >> item    = 'West Texas Intermediate, Cushing' ;
 >> pattern = [item, '.*?*(?<prefix>.*?)(?<price>[\d\.]*)*'] ; 
 >> tokens  = regexp(buffer, pattern, 'names') ;
 tokens = 
    prefix: ''
     price: '92.06'

 >> item    = 'London fixing, spot price' ;
 >> pattern = [item, '.*?*(?<prefix>.*?)(?<price>[\d\.]*)*'] ; 
 >> tokens  = regexp(buffer, pattern, 'names') ;
 tokens = 
    prefix: '&#163;'          % Code, but the forum renders it.
     price: '19.4273'

Cheers,

Cedric

Note that a . is returned for n.a. entries.

EDIT 1: corrected pattern thank to Walter's comment about pound-signs.

EDIT 2: updated with named tokens so we get the prefix (e.g. pound-sign).

[Walter Roberson]

Does this handle the pound-sign currency symbol that can appear between <b> and the number?

[Cedric Wannaz]

Ah thank you Walter, I had not realized that there could be these signs!

[Cedric Wannaz]

Updated so the prefix is extracted (e.g. pound-sign).

Answer 2

[Walter Roberson]

'^<b>.*?\d+(\.\d+)?<\\b>$'

This should allow for the currency symbol, and for the possibility that the decimal point and following digits are not there. The only real "trick" here is the use of .*? to indicate the minimum expansion of repeated . (i.e., match any one character) where .* by itself is "greedy" and would match as many characters as possible.

[Joseph Williams]

That doesn't work. In part because for the source code on the url, the end tags are denoted with a '/' instead of a '\', but after that, it still doesn't returns and empty answer. Do you have any other suggestions?

Best, J. Williams