| Re: the sky is falling down again [message #52352 is a reply to message #52351] |
Wed, 31 January 2007 10:52   |
news.qwest.net
Messages: 137
Registered: September 2005
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Senior Member |
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"Bob Crawford" <Snowman42@gmail.com> wrote in message
news:1170268829.777687.8070@s48g2000cws.googlegroups.com...
> On Jan 31, 1:09 pm, "R.G. Stockwell" <n...@email.please> wrote:
>> Seriously??
>> Does anyone think this is really a problem?
>> I must be missing the point.
>>
>> Who in their right mind would plot a point on a graph
>> (or a line to a point) that is so very very off the axis?
>> That is user error, not a failing in the plot routine to only
>> use 32 bit numbers.
>
> It's certainly counter-intuitive for the line from (0,0) -> (10,10)
> not to pass thru the points.
> ... and it's pretty dangerous to label something like that as 'user
> error'.
I think this is the exact same thing as
IDL> print, 10+2*10^(-7)
10
and complaining that IDL is wrong.
Or,
IDL> for i = 0.0, 9.8 do ....
or
IDL> a = findgen(20)
IDL> print, a[8762938717]
The rule is not to attempt to plot a point that is so far
off the graph that 32 bit calculations do have the required
precision.
anyways, that is how i see it. i.e. as not a flaw in IDL, and
not something they should fix in any priority over some of the
other problems.
> Perhaps the plotting routine should first interpolate the line to the
> extent or the plotted region first - or at least within the limit
> posted by JD.
I don't think we want the routine doing that sort of thing, nor
do I want it to cook toast for me:actually, cook bread, the end
result being toast of course :) .
> Mightn't this be a problem when zooming on on details on a plot? As
> indicated above, it depends on the plot window size as to when this
> misrepresentation will occur.
How can anyone zoom in 8 orders of magnitude (and still have
10 points on the screen)? The length of the array would
probably start to have problems fitting into a 32bit memory address.
Like i said, to see that plot would require a screen 200 km wide.
Thanks for the comments,
Cheers,
bob
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