It seems that the chart API doesn't parse out a date and use it as a domain/range value (this would be nice to have, especially with XSLT processing!) and I've been asked numerous times how I manage to do this. So here it is for those of you out there struggling to get a non- uniform spacing on a domain consisting of dates, simply try the following:
1) For each plot point ([value], [date]) create a conversion to ([value], [epoch seconds]) - most programming languages cater for this or at least some way to convert a dateTime to a numeric value of sorts. 2) Normalize the set: find smallest epoch seconds value in the set, then subtract this amount from each epoch seconds value. equation: ($EpochValue - $MinEpoch) - This just mean using less characters, but is not entirely necessary as the chart can do this for you. 3)generate the chart URL you can see the effect of this grouping in the following example: http://chart.apis.google.com/chart?cht=lxy&chs=800x300&chxt=x,y,y&chxl=0:|2010-08-01|2010-10-15|1:|0|230|2:|umol/l&chxp=2,50&chco=000000,FF0000,0000FF&chm=o,004185,0,-1,10&chds=0,430,14,230&chd=t:0,160,170,180,185,190,198,211,358,371,389,430|14,30,50,77,155,170,88,71,111,131,155,230&chtt=Test+Chart Parameters of the above example are as follows: cht=lxy chs=800x300 chxt=x,y,y chxl=0: 2010-08-01 2010-10-15 1: 0 230 2: umol/l chxp=2,50 chco=000000,FF0000,0000FF chm=o,004185,0,-1,10 chds=0,430,14,230 chd=t:0,160,170,180,185,190,198,211,358,371,389,430 14,30,50,77,155,170,88,71,111,131,155,230 chtt=Test+Chart -- You received this message because you are subscribed to the Google Groups "Google Chart API" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/google-chart-api?hl=en.
