Log

block Log "Output the logarithm (default base e) of the input (input > 0 required)"
    extends Interfaces.SISO;

    parameter Real base = Modelica.Constants.e "Base of logarithm"
        annotation (Evaluate = true);
equation
    y = Modelica.Math.log(u) / Modelica.Math.log(base);

    annotation (
        Icon(
            coordinateSystem(
                preserveAspectRatio = true,
                extent = {
                    {-100, -100}, 
                    {100, 100}}),
            graphics = {
                Line(
                    points = {
                        {-80, -80}, 
                        {-80, 68}},
                    color = {192, 192, 192}), 
                Polygon(
                    points = {
                        {-80, 90}, 
                        {-88, 68}, 
                        {-72, 68}, 
                        {-80, 90}},
                    lineColor = {192, 192, 192},
                    fillColor = {192, 192, 192},
                    fillPattern = FillPattern.Solid), 
                Line(
                    points = {
                        {-80, -80}, 
                        {-79.2, -50.6}, 
                        {-78.4, -37}, 
                        {-77.6, -28}, 
                        {-76.8, -21.3}, 
                        {-75.2, -11.4}, 
                        {-72.8, -1.31}, 
                        {-69.5, 8.08}, 
                        {-64.7, 17.9}, 
                        {-57.5, 28}, 
                        {-47, 38.1}, 
                        {-31.8, 48.1}, 
                        {-10.1, 58}, 
                        {22.1, 68}, 
                        {68.7, 78.1}, 
                        {80, 80}},
                    smooth = Smooth.Bezier), 
                Line(
                    points = {
                        {-90, 0}, 
                        {68, 0}},
                    color = {192, 192, 192}), 
                Polygon(
                    points = {
                        {90, 0}, 
                        {68, 8}, 
                        {68, -8}, 
                        {90, 0}},
                    lineColor = {192, 192, 192},
                    fillColor = {192, 192, 192},
                    fillPattern = FillPattern.Solid), 
                Text(
                    extent = {
                        {-6, -24}, 
                        {66, -72}},
                    lineColor = {192, 192, 192},
                    textString = "log")}),
        Diagram(
            coordinateSystem(
                preserveAspectRatio = true,
                extent = {
                    {-100, -100}, 
                    {100, 100}}),
            graphics = {
                Line(
                    points = {
                        {-80, 80}, 
                        {-88, 80}},
                    color = {192, 192, 192}), 
                Line(
                    points = {
                        {-80, -80}, 
                        {-88, -80}},
                    color = {192, 192, 192}), 
                Line(
                    points = {
                        {-80, -90}, 
                        {-80, 84}},
                    color = {192, 192, 192}), 
                Text(
                    extent = {
                        {-67, 98}, 
                        {-40, 80}},
                    lineColor = {160, 160, 164},
                    textString = "y"), 
                Polygon(
                    points = {
                        {-80, 100}, 
                        {-86, 84}, 
                        {-74, 84}, 
                        {-80, 100}},
                    lineColor = {192, 192, 192},
                    fillColor = {192, 192, 192},
                    fillPattern = FillPattern.Solid), 
                Line(
                    points = {
                        {-100, 0}, 
                        {84, 0}},
                    color = {192, 192, 192}), 
                Polygon(
                    points = {
                        {100, 0}, 
                        {84, 6}, 
                        {84, -6}, 
                        {100, 0}},
                    lineColor = {192, 192, 192},
                    fillColor = {192, 192, 192},
                    fillPattern = FillPattern.Solid), 
                Line(points = {
                    {-80, -80}, 
                    {-79.2, -50.6}, 
                    {-78.4, -37}, 
                    {-77.6, -28}, 
                    {-76.8, -21.3}, 
                    {-75.2, -11.4}, 
                    {-72.8, -1.31}, 
                    {-69.5, 8.08}, 
                    {-64.7, 17.9}, 
                    {-57.5, 28}, 
                    {-47, 38.1}, 
                    {-31.8, 48.1}, 
                    {-10.1, 58}, 
                    {22.1, 68}, 
                    {68.7, 78.1}, 
                    {80, 80}}), 
                Text(
                    extent = {
                        {68, 28}, 
                        {94, 8}},
                    lineColor = {160, 160, 164},
                    textString = "u")}),
        Documentation(info = "<html>\n<p>\nThis blocks computes the output <strong>y</strong> as the\n<em>logarithm</em> to the parameter <em>base</em> of the input <strong>u</strong>:\n</p>\n<pre>\n    y = <strong>log</strong>( u ) / <strong>log</strong>( base );\n</pre>\n<p>\nAn error occurs if the input <strong>u</strong> is\nzero or negative.\n</p>\n\n<p>\n<img src=\"modelica://Modelica/Resources/Images/Math/log.png\"\n     alt=\"log.png\">\n</p>\n\n</html>"));
end Log;