I have data that has error bars and upper limits. (Actually
> they are lower limits, since the Y axis is in stellar
> magnitudes and is inverted.) My suggestion is use a negative
> error value to indicate a limit in which case an arrow would
> be drawn, instead of an error bar. This feature would only
> apply to the case of asymmetric error bars and not to the
> symmetric case. I can produce a patch if this suggestion is
> agreeable.
I certainly don't have a problem with this and would be happy to
include these extensions to the errorbar function. I wonder if the
arrow is the best indicator for a limit, though I can't think of a
better one at the moment. Also, does this handle limits in either
direction (up or down) as well as left to right?
JDH
John Hunter wrote:
"Paul" == Paul Barrett <pebarrett@...149...> writes:
> I have data that has error bars and upper limits. (Actually
> they are lower limits, since the Y axis is in stellar
> magnitudes and is inverted.) My suggestion is use a negative
> error value to indicate a limit in which case an arrow would
> be drawn, instead of an error bar. This feature would only
> apply to the case of asymmetric error bars and not to the
> symmetric case. I can produce a patch if this suggestion is
> agreeable.
I certainly don't have a problem with this and would be happy to
include these extensions to the errorbar function. I wonder if the
arrow is the best indicator for a limit, though I can't think of a
better one at the moment. Also, does this handle limits in either
direction (up or down) as well as left to right?
Arrows are often used to indicate error bars which end outside of the
displayed area of the plot. I would also recommend against using
negative error values to indicate limits instead of errors. It smells of
FORTRAN. 
Limits should probably be implemented by a separate
object/function/whatever.
···
--
Robert Kern
rkern@...170...
"In the fields of hell where the grass grows high
Are the graves of dreams allowed to die."
-- Richard Harter
John Hunter wrote:
“Paul” == Paul Barrett <pebarrett@…149…> writes:
> I have data that has error bars and upper limits. (Actually
> they are lower limits, since the Y axis is in stellar
> magnitudes and is inverted.) My suggestion is use a negative
> error value to indicate a limit in which case an arrow would
> be drawn, instead of an error bar. This feature would only
> apply to the case of asymmetric error bars and not to the
> symmetric case. I can produce a patch if this suggestion is
> agreeable.
I certainly don’t have a problem with this and would be happy to
include these extensions to the errorbar function. I wonder if the
arrow is the best indicator for a limit, though I can’t think of a
better one at the moment. Also, does this handle limits in either
direction (up or down) as well as left to right?
Arrows are often used to indicate error bars which end outside of the
displayed area of the plot. I would also recommend against using
negative error values to indicate limits instead of errors. It smells of
FORTRAN.
Yes, it does smell of FORTRAN. However, my motive for suggesting
negative error values is that it allows the user to specify the length
of the limit arrow and numeric arrays to be used for input. The other
option would be to use a string, e.g.‘limit(2)’, as a marker.
This will complicate the implementation, but that is less of a concern
to me than usability. I think that the ability to specify the
length of the arrow is needed. This could be an optional
parameter though. I’m open to suggestions.
Limits should probably be implemented by a separate
object/function/whatever.
In astronomy, limit data is often associated with data having large
error bars, i.e. they go hand-in-hand. So, a separate function would
essentially duplicate the error bar functionality. I see no
need for this duplicity.
– Paul
···
On 10/7/05, Robert Kern <rkern@…170…> wrote:
Yes, a negative value for the upper error bar will indicate an upper
limit and vice versa for the lower error bar value. The same goes
for left and right limits.
Note that this enhancement will only affect asymmetric error bars and
not symmetric ones, since the latter case doesn’t make much sense to me.
– Paul
···
On 10/7/05, John Hunter <jdhunter@…272…5…> wrote:
> I have data that has error bars and upper limits. (Actually
> they are lower limits, since the Y axis is in stellar
> magnitudes and is inverted.) My suggestion is use a negative
> error value to indicate a limit in which case an arrow would
> be drawn, instead of an error bar. This feature would only
> apply to the case of asymmetric error bars and not to the
> symmetric case. I can produce a patch if this suggestion is
> agreeable.
I certainly don’t have a problem with this and would be happy to
include these extensions to the errorbar function. I wonder if the
arrow is the best indicator for a limit, though I can’t think of a
better one at the moment. Also, does this handle limits in either
direction (up or down) as well as left to right?