--[[ Sample plots using date / time formatting for axes Copyright (C) 2009 Werner Smekal This file is part of PLplot. PLplot is free software you can redistribute it and/or modify it under the terms of the GNU Library General Public License as published by the Free Software Foundation either version 2 of the License, or (at your option) any later version. PLplot is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public License for more details. You should have received a copy of the GNU Library General Public License along with PLplot if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA --]] -- initialise Lua bindings for PLplot examples. dofile("plplot_examples.lua") -- Plot a model diurnal cycle of temperature function plot1() x = {} y = {} xerr1 = {} xerr2 = {} yerr1 = {} yerr2 = {} -- Data points every 10 minutes for 1 day npts = 73 xmin = 0 xmax = 60*60*24 -- Number of seconds in a day ymin = 10 ymax = 20 for i = 1, npts do x[i] = xmax*((i-1)/npts) y[i] = 15 - 5*math.cos(2*math.pi*((i-1)/npts)) -- Set x error bars to +/- 5 minute xerr1[i] = x[i]-60*5 xerr2[i] = x[i]+60*5 -- Set y error bars to +/- 0.1 deg C yerr1[i] = y[i]-0.1 yerr2[i] = y[i]+0.1 end pl.adv(0) -- Rescale major ticks marks by 0.5 pl.smaj(0, 0.5) -- Rescale minor ticks and error bar marks by 0.5 pl.smin(0, 0.5) pl.vsta() pl.wind(xmin, xmax, ymin, ymax) -- Draw a box with ticks spaced every 3 hour in X and 1 degree C in Y. pl.col0(1) -- Set time format to be hours:minutes pl.timefmt("%H:%M") pl.box("bcnstd", 3*60*60, 3, "bcnstv", 1, 5) pl.col0(3) pl.lab("Time (hours:mins)", "Temperature (degC)", "@frPLplot Example 29 - Daily temperature") pl.col0(4) pl.line(x, y) pl.col0(2) pl.errx(xerr1, xerr2, y) pl.col0(3) pl.erry(x, yerr1, yerr2) -- Rescale major / minor tick marks back to default pl.smin(0, 1) pl.smaj(0, 1) end -- Plot the number of hours of daylight as a function of day for a year function plot2() x = {} y = {} -- Latitude for London lat = 51.5 npts = 365 xmin = 0 xmax = npts*60*60*24 ymin = 0 ymax = 24 -- Formula for hours of daylight from -- "A Model Comparison for Daylength as a Function of Latitude and -- Day of the Year", 1995, Ecological Modelling, 80, pp 87-95. for j = 1, npts do x[j] = (j-1)*60*60*24 p = math.asin(0.39795*math.cos(0.2163108 + 2*math.atan(0.9671396*math.tan(0.00860*(j-1-186))))) d = 24 - (24/math.pi)* math.acos( (math.sin(0.8333*math.pi/180) + math.sin(lat*math.pi/180)*math.sin(p)) / (math.cos(lat*math.pi/180)*math.cos(p)) ) y[j] = d end pl.col0(1) -- Set time format to be abbreviated month name followed by day of month pl.timefmt("%b %d") pl.prec(1, 1) pl.env(xmin, xmax, ymin, ymax, 0, 40) pl.col0(3) pl.lab("Date", "Hours of daylight", "@frPLplot Example 29 - Hours of daylight at 51.5N") pl.col0(4) pl.line(x, y) pl.prec(0, 0) end function plot3() x = {} y = {} tstart = 1133395200 npts = 62 xmin = tstart xmax = xmin + npts*60*60*24 ymin = 0 ymax = 5 for i = 1, npts do x[i] = xmin + (i-1)*60*60*24 y[i] = 1 + math.sin(2*math.pi*(i-1)/7) + math.exp(math.min(i-1,npts-i+1)/31) end pl.adv(0) pl.vsta() pl.wind(xmin, xmax, ymin, ymax) pl.col0(1) -- Set time format to be ISO 8601 standard YYYY-MM-DD. Note that this is --equivalent to %f for C99 compliant implementations of strftime. pl.timefmt("%Y-%m-%d") -- Draw a box with ticks spaced every 14 days in X and 1 hour in Y. pl.box("bcnstd", 14*24*60*60,14, "bcnstv", 1, 4) pl.col0(3) pl.lab("Date", "Hours of television watched", "@frPLplot Example 29 - Hours of television watched in Dec 2005 / Jan 2006") pl.col0(4) -- Rescale symbol size (used by plpoin) by 0.5 pl.ssym(0, 0.5) pl.poin(x, y, 2) pl.line(x, y) end function plot4() -- TAI-UTC (seconds) as a function of time. x = {} y = {} -- Continuous time unit is Besselian years from whatever epoch is -- chosen below. Could change to seconds (or days) from the -- epoch, but then would have to adjust xlabel_step below. scale = 365.242198781 -- MJD epoch (see ). -- This is only set for illustrative purposes, and is overwritten -- below for the time-representation reasons given in the -- discussion below. epoch_year = 1858 epoch_month = 11 epoch_day = 17 epoch_hour = 0 epoch_min = 0 epoch_sec = 0. -- To illustrate the time-representation issues of using the MJD -- epoch, in 1985, MJD was roughly 46000 days which corresponds to -- 4e9 seconds. Thus, for the -DPL_DOUBLE=ON case where PLFLT is -- a double which can represent continuous time to roughly 16 -- decimal digits of precision the time-representation error is -- roughly ~400 nanoseconds. Therefore the MJD epoch would be -- acceptable for the plots below in the -DPL_DOUBLE=ON case. -- However, that epoch is obviously not acceptable for the -- -DPL_DOUBLE=OFF case where PLFLT is a float which can represent -- continuous time to only ~7 decimal digits of precision -- corresponding to a time representation error of 400 seconds (!) -- in 1985. For this reason, we do not use the MJD epoch below -- and instead choose the best epoch for each case to minimize -- time-representation issues. for kind = 0, 6 do if kind == 0 then -- Choose midpoint to maximize time-representation precision. epoch_year = 1985 epoch_month = 0 epoch_day = 2 epoch_hour = 0 epoch_min = 0 epoch_sec = 0. pl.configtime(scale, 0., 0., 0, 1, epoch_year, epoch_month, epoch_day, epoch_hour, epoch_min, epoch_sec) xmin = pl.ctime(1950, 0, 2, 0, 0, 0) xmax = pl.ctime(2020, 0, 2, 0, 0, 0) npts = 70*12 + 1 ymin = 0 ymax = 36 time_format = "%Y%" if_TAI_time_format = 1 title_suffix = "from 1950 to 2020" xtitle = "Year" xlabel_step = 10 end if kind==1 or kind==2 then -- Choose midpoint to maximize time-representation precision. epoch_year = 1961 epoch_month = 7 epoch_day = 1 epoch_hour = 0 epoch_min = 0 epoch_sec = 1.64757 pl.configtime(scale, 0., 0., 0, 1, epoch_year, epoch_month, epoch_day, epoch_hour, epoch_min, epoch_sec) xmin = pl.ctime(1961, 7, 1, 0, 0, 1.64757-0.20) xmax = pl.ctime(1961, 7, 1, 0, 0, 1.64757+0.20) npts = 1001 ymin = 1.625 ymax = 1.725 time_format = "%S%2%" title_suffix = "near 1961-08-01 (TAI)" xlabel_step = 0.05/(scale*86400) if kind==1 then if_TAI_time_format = 1 xtitle = "Seconds (TAI)" else if_TAI_time_format = 0 xtitle = "Seconds (TAI) labelled with corresponding UTC" end end if kind==3 or kind==4 then -- Choose midpoint to maximize time-representation precision. epoch_year = 1963 epoch_month = 10 epoch_day = 1 epoch_hour = 0 epoch_min = 0 epoch_sec = 2.6972788 pl.configtime(scale, 0., 0., 0, 1, epoch_year, epoch_month, epoch_day, epoch_hour, epoch_min, epoch_sec) xmin = pl.ctime(1963, 10, 1, 0, 0, 2.6972788-0.20) xmax = pl.ctime(1963, 10, 1, 0, 0, 2.6972788+0.20) npts = 1001 ymin = 2.55 ymax = 2.75 time_format = "%S%2%" title_suffix = "near 1963-11-01 (TAI)" xlabel_step = 0.05/(scale*86400) if kind==3 then if_TAI_time_format = 1 xtitle = "Seconds (TAI)" else if_TAI_time_format = 0 xtitle = "Seconds (TAI) labelled with corresponding UTC" end end if kind==5 or kind==6 then -- Choose midpoint to maximize time-representation precision. epoch_year = 2009 epoch_month = 0 epoch_day = 1 epoch_hour = 0 epoch_min = 0 epoch_sec = 34. pl.configtime(scale, 0., 0., 0, 1, epoch_year, epoch_month, epoch_day, epoch_hour, epoch_min, epoch_sec) xmin = pl.ctime(2009, 0, 1, 0, 0, 34-5) xmax = pl.ctime(2009, 0, 1, 0, 0, 34+5) npts = 1001 ymin = 32.5 ymax = 34.5 time_format = "%S%2%" title_suffix = "near 2009-01-01 (TAI)" xlabel_step = 1/(scale*86400) if kind==5 then if_TAI_time_format = 1 xtitle = "Seconds (TAI)" else if_TAI_time_format = 0 xtitle = "Seconds (TAI) labelled with corresponding UTC" end end for i = 1, npts do x[i] = xmin + (i-1)*(xmax-xmin)/(npts-1) tai = x[i] pl.configtime(scale, 0., 0., 0, 1, epoch_year, epoch_month, epoch_day, epoch_hour, epoch_min, epoch_sec) tai_year, tai_month, tai_day, tai_hour, tai_min, tai_sec = pl.btime(tai) -- Calculate residual using tai as the epoch to nearly maximize time-representation precision. pl.configtime(scale, 0., 0., 0, 1, tai_year, tai_month, tai_day, tai_hour, tai_min, tai_sec) -- Calculate continuous tai with new epoch. tai = pl.ctime(tai_year, tai_month, tai_day, tai_hour, tai_min, tai_sec) -- Calculate broken-down utc (with leap seconds inserted) from continuous tai with new epoch. pl.configtime(scale, 0., 0., 2, 1, tai_year, tai_month, tai_day, tai_hour, tai_min, tai_sec) utc_year, utc_month, utc_day, utc_hour, utc_min, utc_sec = pl.btime(tai) -- Calculate continuous utc from broken-down utc using same epoch as for the continuous tai. pl.configtime(scale, 0., 0., 0, 1, tai_year, tai_month, tai_day, tai_hour, tai_min, tai_sec) utc = pl.ctime(utc_year, utc_month, utc_day, utc_hour, utc_min, utc_sec) -- Convert residuals to seconds. y[i]=(tai-utc)*scale*86400. end pl.adv(0) pl.vsta() pl.wind(xmin, xmax, ymin, ymax) pl.col0(1) if if_TAI_time_format ~= 0 then pl.configtime(scale, 0., 0., 0, 1, epoch_year, epoch_month, epoch_day, epoch_hour, epoch_min, epoch_sec) else pl.configtime(scale, 0., 0., 2, 1, epoch_year, epoch_month, epoch_day, epoch_hour, epoch_min, epoch_sec) end pl.timefmt(time_format) pl.box("bcnstd", xlabel_step, 0, "bcnstv", 0., 0) pl.col0(3) title = "@frPLplot Example 29 - TAI-UTC " .. title_suffix pl.lab(xtitle, "TAI-UTC (sec)", title) pl.col0(4) pl.line(x, y) end end ---------------------------------------------------------------------------- -- main -- -- Draws several plots which demonstrate the use of date / time formats for -- the axis labels. -- Time formatting is done using the system strftime routine. See the -- documentation of this for full details of the available formats. -- -- 1) Plotting temperature over a day (using hours / minutes) -- 2) Plotting -- -- Note: Times are stored as seconds since the epoch (usually 1st Jan 1970). -- ---------------------------------------------------------------------------- -- Parse command line arguments pl.parseopts(arg, pl.PL_PARSE_FULL) -- Initialize plplot pl.init() -- Change the escape character to a '@' instead of the default '#' pl.sesc('@') plot1() plot2() plot3() plot4() -- Don't forget to call plend() to finish off! pl.plend()