Benchmarking function sun_angles() [updated]

As far as I know there are in CRAN four R packages implementing the computations for the position of the sun and times of sunrise and sunset: ‘photobiology’, ‘fishmethods’, ‘solartime’ and ‘suncalc’.

The functions sun_angles() and day_night() from package ‘photobiology’ use Meeus equations as used by NOAA Solar Calculator https://www.esrl.noaa.gov/gmd/grad/solcalc/ which could be more precise than those in NOAA’s Excel worksheet which implement a simplified version of the Meeus equations especially for far into the past or far into the future calculations. The approximations based on Meuus equations are very good for years between 1800 and 2100 and results should still be sufficiently accurate for the range from -1000 to 3000 as long as the computation of Julian dates is correct. The Excel implementation is only valid for dates between 1901 and 2099 because of how Julian dates are computed in Excel.

Function astrocalc4r() from package ‘fishmethods’ also implements Meeus equations (the authors work at NOAA). Function computeSunPosition() from package ‘solartime’ uses unspecified equations and function getSunlightPosition() is an R interface to the ‘suncalc.js’ library, part of the ‘SunCalc.net’ project <http://suncalc.net>.

Function computeSunPosition() from package ‘solartime’ uses unspecified equations and function getSunlightPosition() is an R interface to the ‘suncalc.js’ library, part of the ‘SunCalc.net’ project <http://suncalc.net>.

UPDATED on 2019-04-24

I have noticed significant differences in the values returned by equivalent functions from different packages. Up to now the tests on the functions of my own package ‘photobiology’ have revealed only very small mismatches to the NOAA Solar Calculator. These small errors, noticeable for dates far from the present, were due to the use of base R’s julian() function, which is not designed to be precise enough for astronomical calculations. The code now in the repository at Bitbucket has been revised to use Meuus’ algorithm for the calculation of Julian days removing this source of  small discrepancies.

In contrast, while testing ‘photobiology’ against other packages, I seem to have found a bug in function astrocalc4r() from R package ‘fishmethods’.

A minimal example follows:

By only changing the hour passed as argument different times for sunrise, sunset and daylength are returned even though the day is the same. The differences are larger at high than at low latitudes. The maximum difference for the example above is 1/4 h for daylength. Comparison against the NOAA Solar Calculator shows even larger differences.

(The bug has been reported to the maintainer of package ‘fishmethods’.)

Continue reading

ggpmisc 0.3.1

After the previous major update to ‘ggpmisc’ (0.3.0), a follow up (0.3.1) with multiple new features and smoothed rough edges for some of the features added in version 3.0.0. Package documentation is available at https://docs.r4photobiology.info/ggpmisc/ as a web site.

The enhancements in this and the previous update to ‘ggpmisc’ are made possible by changes to ‘ggplot2’ (>= 3.0.0) made while adding support for sf (simple features).

The functions in ‘ggpmisc’ (>= 0.3.1) are related to different kinds of annotations and insets in ggplots. Annotations of plots with fitted-model equations, fit diagnosis, ANOVA and summary tables, highlighting and labelling of peaks and valleys in curves, and local density-based highlighting or labelling in scatter plots. Additionally specializations of the ggplot() constructor allow on-the-fly conversion of time-series. Two new geoms join geom_table() added in version 0.3.0, geom_plot() and geom_grob(). These three geoms make it possible to add tables, ggplots and arbitrary graphical objects (grobs) as insets to plots respecting the the Grammar of Graphics paradigm.

Inset plot showing means per group.
Inset grobs

A set of new geometries produce marginal annotations: geom_x_margin_point(), geom_y_margin_point(), geom_x_margin_arrow(), geom_y_margin_arrow(), geom_x_margin_grob() and geom_y_margin_grob().

Marginal “points” showing means per group.

Another novel feature is based on the addition of two new aesthetics npcx and npcy, the corresponding scales scale_npcx_continuous() and scale_npcy_continuous(), and several new geometries that make use of then: geom_text_npc(), geom_label_npc(), geom_table_npc(), geom_plot_npc() and geom_grob_npc(). These allow to position insets and annotations relative to the dimensions of the plotting area instead of using native data units. Using "npc" units is more natural for labels or insets that are not directly related to data but that look better if positioned consistently across multiple panels or multiple separately produced plots. One improvement to the stats from earlier versions of ‘ggpmisc’ is the use of these new geoms to achieve more consistent location for insets and labels.

Quadrant counts with panels.
Fitted equations in panels with free y limits.
Inset tables at different positions in different panels.

As in the announcement of the previous version, I have included some example plots taken from the documentation of the package. In all cases annotations are generated automatically, but formatting is flexible.

NOTE: The new version of ‘ggpmisc’ will be soon submitted to CRAN .

photobiologyWavebands 0.4.3

The main changes from version 0.4.2 the previous CRAN release, are:

  • Add waveband definitions for non-standard split of the UVA band with constructors UVAsw() and UVAlw().
  • Add two new definitions of far-red as used in remote sensing: "RedEdge20" and "RedEdge40".
  • Minor updates to documentation.

Documentation web site at https://docs.r4photobiology.info/photobiologyWavebands/.

NOTE: The updated package is available through CRAN.

Please raise issues concerning bugs or enhancements to this package through Bitbucket at https://bitbucket.org/aphalo/photobiologywavebands/issues

photobiologySun 0.4.1

The main changes from version 0.4.0, the most recent version are:

  • Rebuild data objects with ‘photobiology’ 0.9.26 to fix minor bugs.
  • Replace non-ASCII characters in documentation.

Documentation web site at https://docs.r4photobiology.info/photobiologySun/.

NOTE: The updated package is available through CRAN.

Please raise issues concerning bugs or enhancements to this package through Bitbucket at https://bitbucket.org/aphalo/photobiologysun/issues