How to interpret ButtonDownFcn event data for axis which limit is datetime?

This seems like something obvious but I've searched for this all afternoon and can't come up with anything that addresses my issue. I've been struggling with my buttondownfcn callback on an axes which xaxis is defined in datetime.

K>> ax.XAxis

ans = 

    DatetimeRuler with properties:

               Limits: [Aug 21, 2017, 21:00    Aug 21, 2017, 22:45]
           TickValues: [Aug 21, 2017, 21:00    Aug 21, 2017, 21:15    Aug 21, 2017, 21:30    Aug 21, 2017, 21:45    Aug 21, 2017, 22:00    Aug 21, 2017, 22:15    Aug 21, 2017, 22:30    Aug 21, 2017, 22:45]
      TickLabelFormat: 'HH:mm'

    Show all properties

The eventinformation comes in as

K>> eventdata

eventdata = 

    Hit with properties:

                 Button: 1
      IntersectionPoint: [0.927083313465118 5.139902343750000e+02 -1]
                 Source: [1×1 Axes]
              EventName: 'Hit'

I've read that is the "location of last button click, in axes data units", but the x value doesn't look like a datenum. I thought it might be an offset from the axis limit but

K>> ax.XLim(1)+eventdata.IntersectionPoint(1)

ans = 

    datetime

     Aug 22, 2017, 19:14

is not where I picked. I picked as closed to the 22:15 tick mark (in the attached image) as I could. It's close but there's an origin somewhere that I seem to be missing.

Can anyone shed some light on this?

[Walter Roberson]

As an experiment, try

ax.XLim(1) + diff(ax.XLim) * eventdata.IntersectionPoint(1)

[Scott Senften]

Sadly, no, that didn't work

On the left side which should be 21:00, the intersection point is 0.875

in mouseButtonPressed
248             disp(['pick: ', datestr(ax.XLim(1) + diff(ax.XLim) * eventdata.IntersectionPoint(1))])
K>> eventdata.IntersectionPoint(1)

ans =

     0.875000000000000

pick: 21-Aug-2017 22:31:52

On the rightside which should be 22:45, the intersection point is 0.9479.

in mouseButtonPressed
248             disp(['pick: ', datestr(ax.XLim(1) + diff(ax.XLim) * eventdata.IntersectionPoint(1))])
K>> eventdata.IntersectionPoint(1)

ans =

     0.947916686534882

pick: 21-Aug-2017 22:39:31

[Campion Loong]

Hi Scott,

Could you give these functions a try and see if they suit your needs. Looking at your question, num2ruler is a more likely candidate. You'll need to pass it the specific ruler you are working with:

num2ruler

ruler2num

[Scott Senften]

Campion, thank you. At first blush, that seems to be exactly what I was looking for. Specifically, for my use case, to convert a button down event on the axes to the appropriate timedate variable, I used:

          function mouseButtonPressed(this, object, eventdata, ax)

               disp('in mouseButtonPressed')
              eventdata.IntersectionPoint
              disp(['pick: ', datestr(num2ruler(eventdata.IntersectionPoint(1), ax.XAxis))])
          end

I realize that in this instance the inclusion of 'ax' is redundant as it would be the 'object' as well.

[Campion Loong]

You're welcome Scott. Hope it does solve your needs at the end.

On a side note, since you have a datetime coming out of num2ruler, you can directly convert it to text using char(...) or, if you have 16b or later, string(...)

[Walter Roberson]

Campion Loong, I suggest you copy your responses to be an Answer so they can be Accepted.

Answer 1

[Campion Loong]

As Walter suggested, pasting my comment as answer:

Give these functions a try and see if they suit your needs. Looking at your question, num2ruler is a more likely candidate. You'll need to pass it the specific ruler you are working with:

num2ruler

ruler2num

[Scott Senften]

          function mouseButtonPressed(this, object, eventdata, ax)

               disp('in mouseButtonPressed')
              eventdata.IntersectionPoint
              disp(['pick: ', datestr(num2ruler(eventdata.IntersectionPoint(1), ax.XAxis))])
          end

[Joris Brouwer]

Thanks! This was not trivial once I zoomed in or panned the figure. Should be in Matlab documentation itself for the ButtonDownFcn. But this works exactly as intended.