The manual still seems to be built correctly after these changes. (At least, I'm not aware of any reports about the contrary.)

Closing report as fixed.

If someone is interested in making the changes that Lars suggested in comment #5, we should open a separate report.

Looks good for me, thanks for doing the formatting.

What do you think about datetick() throwing a warning in qt and fltk, pointing to this text, when the axes' limits look like being affected? Some simple heuristics, like checking if pixel resolution is way better than numerical resolution for the singles?

"Warning: For timestamps in the current range the plot resolution is worse than 45 minutes. The plot may look distorted. See (link here) for a possible workaround."

Or even make plot() and other functions check for some scaled difference between data(:) and single(data(:))? But that's a lot of work in many functions...

What do you think about this? Where should it be located in doc/interpreter/plot.txi ?

The limitation to single precision in particular applies to plots of timeseries against serial dates as used by the datenum(), datestr(), datestruct(), and datetick() functions.

Serial dates encode timestamps as days elapsed since the year zero with hours, minutes, seconds as the fractional part. On Dec. 31. 1999 the serial date representation was 730485. A double precision variable with this integer part allows for a resolution in its fractional part of 1.2e-10, representing about 5 microseconds. But with single precision this is reduced to about 0.06, representing 45 minutes. Any attempt to plot timestamped data with finer granularity will result in a distorted graph.

As a workaround one can subtract 2000 years, i.e. datenum(2000,0,0) or 730485 from the time values. Due to the fact that the calendar structure repeats every 2000 years, the relation between year, month, day of month and day of week will stay unchanged and the ticks and ticklabels produced by the datetick() function will still be correct. Only years will lack the millennium digit, thus "2020" will be printed as "20".

Just replace plot (t, x) with plot (t - 730485, x)

#timestamps of 24 hours in one minute steps
t = datenum(2020,1,1):(1/1440):datenum(2020,1,2);

#some example timeseries data
x = -cos(2*pi*t) + rand(size(t)) / 10;

subplot(1,2,1)
plot(t,x)
datetick x
xlabel "serial date"
title "problem"

subplot(1,2,2)
plot(t - 730485,x)
datetick x
xlabel "2000 years off"
title "workaround"

Me and my students are really often hit by this bug when plotting time series with serial dates on the time-axis. It will inevitably occur when you plot recent timestamped data with better than minute resolution or so. I had provided a striking example in bug #32980.

So I suggest to include this specific issue in the documentation, together with the simple proposed workaround to subtract datenum(2000,0,0) from the date values, because luckily our calendar repeats every 2000 years. Month, days and even weekdays stay correct this way.

The only minor issue then is that dateticklabels may state the year as "0020". Perhaps the routines to automatically label the date axis could be temporally modified to leave out the century digits if they equal to "00"?

And of course you have to keep in mind the offset in callbacks...