Module:Weather

-- Efficient (fast) functions to implement cells in tables of weather data. Temperature conversion is built-in, but for simplicity, temperatures are assumed to be for habitable locations (from -100 to 100 °C).

local MINUS = '−' -- Unicode U+2212 MINUS SIGN

local function temperature_style(palette, value, out_rgb) -- Return style for a table cell based on the given value which -- should be a temperature in °C. local function style(bg, fg) local min, max = unpack(palette.white or { -23, 35 }) if not fg and value and (value = max) then fg = 'FFFFFF' end if fg then fg = 'color:#' .. fg .. ';'		else fg = '' end return 'style="background:#' .. bg .. ';' .. fg .. ' font-size:100%;"' end if type(value) ~= 'number' then return style('FFFFFF', '000000') end local rgb = out_rgb or {} for i, v in ipairs(palette) do		local a, b, c, d = unpack(v) if value <= a then rgb[i] = 0 elseif value < b then rgb[i] = (value - a) * 255 / (b - a)		elseif value <= c then rgb[i] = 255 elseif value < d then rgb[i] = 255 - ( (value - c) * 255 / (d - c) ) else rgb[i] = 0 end end return style(string.format('%02X%02X%02X', rgb[1], rgb[2], rgb[3])) end

local function format_cell(palette, value, intext, outtext) -- Return one line of wikitext to make a cell in a table. if not value then return '|\n' end local text if outtext then text = intext .. ' (' .. outtext .. ')' else text = intext end return '| ' .. temperature_style(palette, value) .. ' | ' .. text .. '\n' end

local function process_temperature(intext, inunit, swap) --	Convert °C to °F or vice versa, assuming the temperature is for a			habitable location, well inside the range -100 to 100 °C.			That simplifies determining precision and formatting (no commas are needed).			Return (celsius_value, intext, outtext) if valid; otherwise return nil.			The returned input and output are swapped if requested.			Each returned string has a Unicode MINUS as sign, if negative. local invalue = tonumber(intext) if not invalue then return nil end local integer, dot, decimals = intext:match('^%s*%-?(%d+)(%.?)(%d*)%s*$') if not integer then return nil end if invalue < 0 then intext = MINUS .. integer .. dot .. decimals end local outtext if inunit == 'C' or inunit == 'F' then local celsius_value, outvalue if inunit == 'C' then outvalue = invalue * (9/5) + 32 celsius_value = invalue else outvalue = (invalue - 32) * (5/9) celsius_value = outvalue end local precision = dot == '' and 0 or #decimals outtext = string.format('%.' .. precision .. 'f', math.abs(outvalue) + 2e-14) if outvalue < 0 and tonumber(outtext) ~= 0 then -- Don't show minus if result is negative but rounds to zero. outtext = MINUS .. outtext end if swap then return celsius_value, outtext, intext end return celsius_value, intext, outtext end -- LATER Think about whether a no-conversion option would be useful. return invalue, intext, outtext end

local function temperature_row(palette, row, inunit, swap) --	Return 13 lines specifying the style/content of 13 table cells.	Input is 13 space-separated words, each a number (°C or °F).	Any word that is not a number gives a blank cell ("M" for a missing cell).	Any excess words are ignored.	Function Input   Output	CtoF        C       C/F	FfromC      C       F/C	CfromF      F       C/F	FtoC        F       F/C local nrcol = 13 local results, n = {}, 0 for word in row:gmatch('%S+') do		n = n + 1 if n > nrcol then break end results[n] = format_cell(palette, process_temperature(word, inunit, swap)) end for i = n + 1, nrcol do		results[i] = format_cell end return table.concat(results) end

local palettes = { -- A background color entry in a palette is a table of four numbers, -- say { 11, 22, 33, 44 } (values in °C). -- That means the color is 0 below 11 and above 44, and is 255 from 22 to 33. -- The color rises from 0 to 255 between 11 and 22, and falls between 33 and 44. cool = { { -42.75,  4.47, 41.5, 60   },		{ -42.75,   4.47,  4.5, 41.5 },		{ -90  , -42.78,  4.5, 23   },		white = { -23.3, 37.8 }, },	cool2 = { { -42.75,  4.5, 41.5, 56   },		{ -42.75,   4.5 ,  4.5, 41.5 },		{ -90   , -42.78,  4.5, 23   },		white = { -23.3, 35 }, },	cool2avg = { { -38,  4.5, 25 , 45   },		{ -38,   4.5,  4.5, 30   },		{ -70, -38  ,  4.5, 23   },		white = { -23.3, 25 }, }, }

local function temperatures(frame, inunit, swap) local palette = palettes[frame.args.palette] or palettes.cool return temperature_row(palette, frame.args[1], inunit, swap) end

local function CtoF(frame) return temperatures(frame, 'C') end

local function CfromF(frame) return temperatures(frame, 'F', true) end

local function FtoC(frame) return temperatures(frame, 'F') end

local function FfromC(frame) return temperatures(frame, 'C', true) end

local chart = [[

]]

local function show(frame) --	For testing, return wikitext to show graphs of how the red/green/blue colors			vary with temperature, and a table of the resulting colors. local function collection -- Return a table to hold items. return { n = 0, add = function (self, item) self.n = self.n + 1 self[self.n] = item end, join = function (self, sep) return table.concat(self, sep) end, }	end local function make_chart(result, color, xvalues, yvalues) result:add('\n') result:add(frame:preprocess((chart:gsub('__[A-Z]+', { __COLOR = color, __XVALUES = xvalues:join(','), __YVALUES = yvalues:join(','), }))))	end local function with_minus(value) if value < 0 then return MINUS .. tostring(-value) end return tostring(value) end local args = frame.args local first = args[1] or -90 local last = args[2] or 59 local palette = palettes[args.palette] or palettes.cool local xvals, reds, greens, blues = collection, collection, collection, collection local wikitext = collection wikitext:add( class="wikitable" 	) local columns = 0 for celsius = first, last do		local rgb = {} local style = temperature_style(palette, celsius, rgb) local R = math.floor(rgb[1]) local G = math.floor(rgb[2]) local B = math.floor(rgb[3]) xvals:add(celsius) reds:add(R) greens:add(G) blues:add(B) wikitext:add('| ' .. style .. ' | ' .. with_minus(celsius) .. '\n') columns = columns + 1 if columns >= 10 then columns = 0 wikitext:add('|-\n') end end wikitext:add('|}\n') make_chart(wikitext, 'Red', xvals, reds) make_chart(wikitext, 'Green', xvals, greens) make_chart(wikitext, 'Blue', xvals, blues) return wikitext:join end

return { CtoF = CtoF, CfromF = CfromF, FtoC = FtoC, FfromC = FfromC, show = show, }