% language=us

\environment luametafun-style

\startcomponent luametafun-function

\startchapter[title={Function}]

It is tempting to make helpers that can do a lot. However, that also means that
we need to explain a lot. Instead it makes more sense to have specific helpers
and just make another one when needed. Rendering functions falls into this
category. At some point users will come up with specific cases that other users
can use. Therefore, the solution presented here is not the ultimate answer. We
start with a simple example:

\startbuffer[1]
\startMPcode{doublefun}
    draw lmt_function [
        xmin =  0, xmax = 20, xstep = .1,
        ymin = -2, ymax =  2,

        sx = 1mm, xsmall = 80, xlarge = 20,
        sy = 4mm, ysmall = 40, ylarge =  4,

        linewidth = .025mm, offset = .1mm,

        code = "1.5 * math.sind (50 * x - 150)",
    ]
        xsized 8cm
    ;
\stopMPcode
\stopbuffer

\startplacefigure
    \getbuffer[1]
\stopplacefigure

This image is defined as follows:

\typebuffer[1][option=TEX]

\startbuffer[2]
\startMPcode{doublefun}
    draw lmt_function [
        xmin =  0, xmax = 20, xstep = .1,
        ymin = -2, ymax =  2,

        sx = 1mm, xsmall = 80, xlarge = 20,
        sy = 4mm, ysmall = 40, ylarge =  4,

        linewidth = .025mm, offset = .1mm,

        xticks    = "bottom",
        yticks    = "left",
        xlabels   = "nolimits",
        ylabels   = "yes",
        code      = "1.5 * math.sind (50 * x - 150)",
      % frame     = "ticks",
        frame     = "sticks",
        ycaption  = "\strut \rotate[rotation=90]{something vertical, using $\sin{x}$}",
        xcaption  = "\strut something horizontal",
        functions = {
            [ xmin =  1.0, xmax =  7.0, close = true, fillcolor = "darkred" ],
            [ xmin =  7.0, xmax = 12.0, close = true, fillcolor = "darkgreen" ],
            [ xmin = 12.0, xmax = 19.0, close = true, fillcolor = "darkblue" ],
            [
                drawcolor = "darkyellow",
                drawsize  = 2
            ]
        }
    ]
        xsized TextWidth
    ;
\stopMPcode
\stopbuffer

We can draw multiple functions in one go. The next sample split the drawing over
a few ranges and is defined as follows; in \in {figure} [function:2] we see the
result.

\typebuffer[2][option=TEX]


\startplacefigure[reference=function:2]
    \getbuffer[2]
\stopplacefigure

Instead of the same function, we can draw different ones and when we use transparency
we get nice results too.

\startbuffer[3]
\definecolor[MyColorR][r=.5,t=.5,a=1]
\definecolor[MyColorG][g=.5,t=.5,a=1]
\definecolor[MyColorB][b=.5,t=.5,a=1]

\startMPcode{doublefun}
    draw lmt_function [
        xmin =  0, xmax = 20, xstep = .1,
        ymin = -1, ymax =  1,

        sx = 1mm, xsmall = 80, xlarge = 20,
        sy = 4mm, ysmall = 40, ylarge =  4,

        linewidth = .025mm, offset = .1mm,

        functions = {
            [
                code      = "math.sind (50 * x - 150)",
                close     = true,
                fillcolor = "MyColorR"
            ],
            [
                code      = "math.cosd (50 * x - 150)",
                close     = true,
                fillcolor = "MyColorB"
            ]
        },
    ]
        xsized TextWidth
    ;
\stopMPcode
\stopbuffer

\typebuffer[3][option=TEX]

\startplacefigure[reference=function:3]
    \getbuffer[3]
\stopplacefigure

It is important to choose a good step. In \in {figure} [function:4] we show 4
variants and it is clear that in this case using straight line segments is better
(or at least more efficient with small steps).

\startbuffer[4a]
\startMPcode{doublefun}
    draw lmt_function [
        xmin =  0, xmax = 10, xstep = .1,
        ymin = -1, ymax =  1,

        sx = 1mm, sy = 4mm,

        linewidth = .025mm, offset = .1mm,

        code  = "math.sind (50 * x^2 - 150)",
        shape = "curve"
    ]
        xsized .45TextWidth
    ;
\stopMPcode
\stopbuffer

\startbuffer[4b]
\startMPcode{doublefun}
    draw lmt_function [
        xmin =  0, xmax = 10, xstep = .01,
        ymin = -1, ymax =  1,

        sx = 1mm, sy = 4mm,

        linewidth = .025mm, offset = .1mm,

        code  = "math.sind (50 * x^2 - 150)",
        shape = "curve"
    ]
        xsized .45TextWidth
    ;
\stopMPcode
\stopbuffer

\startbuffer[4c]
\startMPcode{doublefun}
    draw lmt_function [
        xmin =  0, xmax = 10, xstep = .1,
        ymin = -1, ymax =  1,

        sx = 1mm, sy = 4mm,

        linewidth = .025mm, offset = .1mm,

        code  = "math.sind (50 * x^2 - 150)",
        shape = "line"
    ]
        xsized .45TextWidth
    ;
\stopMPcode
\stopbuffer

\startbuffer[4d]
\startMPcode{doublefun}
    draw lmt_function [
        xmin =  0, xmax = 10, xstep = .01,
        ymin = -1, ymax =  1,

        sx = 1mm, sy = 4mm,

        linewidth = .025mm, offset = .1mm,

        code  = "math.sind (50 * x^2 - 150)",
        shape = "line"
    ]
        xsized .45TextWidth
    ;
\stopMPcode
\stopbuffer

\typebuffer[4a][option=TEX]

\startplacefigure[reference=function:4]
    \startcombination[2*2]
        {\getbuffer[4a]} {\type {xstep=.10} and \type {shape="curve"}}
        {\getbuffer[4b]} {\type {xstep=.01} and \type {shape="curve"}}
        {\getbuffer[4c]} {\type {xstep=.10} and \type {shape="line"}}
        {\getbuffer[4d]} {\type {xstep=.01} and \type {shape="line"}}
    \stopcombination
\stopplacefigure

You can manipulate the axis (a bit) by tweaking the first and last ticks. In the
case of \in {figure} [function:5] we also put the shape on top of the axis.

\startbuffer[5]
\startMPcode{doublefun}
    draw lmt_function [
        xfirst =  9, xlast = 21, ylarge = 2, ysmall = 1/5,
        yfirst = -1, ylast =  1, xlarge = 2, xsmall = 1/4,

        xmin = 10, xmax = 20, xstep = .25,
        ymin = -1, ymax =  1,

        drawcolor = "darkmagenta",
        shape     = "steps",
        code      = "0.5 * math.random(-2,2)",
        linewidth = .025mm,
        offset    = .1mm,
        reverse   = true,
    ]
        xsized TextWidth
    ;
\stopMPcode
\stopbuffer

\typebuffer[5][option=TEX]

\startplacefigure[reference=function:5]
    \getbuffer[5]
\stopplacefigure

The whole repertoire of parameters (in case of doubt just check the source code as this
kind of code is not that hard to follow) is:

\starttabulate[|T|T|T|p|]
\FL
\BC name        \BC type    \BC default \BC comment \NC \NR
\ML
\NC sx          \NC numeric \NC 1mm    \NC horizontal scale factor \NC \NR
\NC sy          \NC numeric \NC 1mm    \NC vertical scale factor \NC \NR
\NC offset      \NC numeric \NC 0      \NC \NC \NR
\NC xmin        \NC numeric \NC 1      \NC \NC \NR
\NC xmax        \NC numeric \NC 1      \NC \NC \NR
\NC xstep       \NC numeric \NC 1      \NC \NC \NR
\NC xsmall      \NC numeric \NC        \NC optional step of small ticks \NC \NR
\NC xlarge      \NC numeric \NC        \NC optional step of large ticks \NC \NR
\NC xlabels     \NC string  \NC no     \NC \type {yes}, \type {no} or \type {nolimits} \NC \NR
\NC xticks      \NC string  \NC bottom \NC possible locations are \type {top}, \type {middle} and \type {bottom} \NC \NR
\NC xcaption    \NC string  \NC        \NC \NC \NR
\NC ymin        \NC numeric \NC 1      \NC \NC \NR
\NC ymax        \NC numeric \NC 1      \NC \NC \NR
\NC ystep       \NC numeric \NC 1      \NC \NC \NR
\NC ysmall      \NC numeric \NC        \NC optional step of small ticks \NC \NR
\NC ylarge      \NC numeric \NC        \NC optional step of large ticks \NC \NR
\NC xfirst      \NC numeric \NC        \NC left of \type {xmin} \NC \NR
\NC xlast       \NC numeric \NC        \NC right of \type {xmax} \NC \NR
\NC yfirst      \NC numeric \NC        \NC below \type {ymin} \NC \NR
\NC ylast       \NC numeric \NC        \NC above \type {ymax} \NC \NR
\NC ylabels     \NC string  \NC no     \NC \type {yes}, \type {no} or \type {nolimits} \NC \NR
\NC yticks      \NC string  \NC left   \NC possible locations are \type {left}, \type {middle} and \type {right} \NC \NR
\NC ycaption    \NC string  \NC        \NC \NC \NR
\NC code        \NC string  \NC        \NC \NC \NR
\NC close       \NC boolean \NC false  \NC \NC \NR
\NC shape       \NC string  \NC curve  \NC or \type {line} \NC \NR
\NC fillcolor   \NC string  \NC        \NC \NC \NR
\NC drawsize    \NC numeric \NC 1      \NC \NC \NR
\NC drawcolor   \NC string  \NC        \NC \NC \NR
\NC frame       \NC string  \NC        \NC options are \type {yes}, \type {ticks} and \type {sticks} \NC \NR
\NC linewidth   \NC numeric \NC .05mm  \NC \NC \NR
\NC pointsymbol \NC string  \NC        \NC like type {dots} \NC \NR
\NC pointsize   \NC numeric \NC 2      \NC \NC \NR
\NC pointcolor  \NC string  \NC        \NC \NC \NR
\NC xarrow      \NC string  \NC        \NC \NC \NR
\NC yarrow      \NC string  \NC        \NC \NC \NR
\NC reverse     \NC boolean \NC false  \NC when \type {true} draw the function between axis and labels \NC \NR
\LL
\stoptabulate

\stopchapter

\stopcomponent
