function plot(equation) {
var graph;
var xPadding = 30;
var yPadding = 30;
var data = {
values : [{
X : "1",
Y : 15
}, {
X : "2",
Y : 35
}, {
X : "3",
Y : 60
}, {
X : "4",
Y : 14
}, {
X : "5",
Y : 20
}, {
X : "6",
Y : -30
},
]
};
// Returns the max Y value in our data list
function getMaxY() {
var max = 0;
for (var i = 0; i < data.values.length; i++) {
if (data.values[i].Y > max) {
max = data.values[i].Y;
}
}
max += 10 - max % 10;
return max;
}
var scaleA = 1.4;
// Return the x pixel for a graph point
function getXPixel(val) {
return ((graph.width() / scaleA - xPadding) / data.values.length) * val + (xPadding * 1.5);
}
// Return the y pixel for a graph point
function getYPixel(val) {
return graph.height() / scaleA - (((graph.height() / scaleA - yPadding) / getMaxY()) * val) - yPadding;
}
graph = $('#graph');
var c = graph[0].getContext('2d');
c.clearRect(0,0,graph[0].width,graph[0].height);
c.lineWidth = 2;
c.strokeStyle = '#333';
c.font = 'italic 8pt sans-serif';
c.textAlign = "center";
// Draw the axises
c.beginPath();
c.moveTo(xPadding, 0);
c.lineTo(xPadding, graph.height() / scaleA - yPadding);
c.lineTo(graph.width(), graph.height() / scaleA - yPadding);
c.stroke();
// Draw the X value texts
for (var i = 0; i < data.values.length; i++) {
c.fillText(data.values[i].X, getXPixel(i), graph.height() / scaleA - yPadding + 20);
}
// Draw the Y value texts
c.textAlign = "right"
c.textBaseline = "middle";
for (var i = 0; i < getMaxY(); i += 10) {
c.fillText(i, xPadding - 10, getYPixel(i));
}
c.strokeStyle = '#f00';
// Draw the line graph
c.beginPath();
c.moveTo(getXPixel(0), getYPixel(equation(0)));
for (var i = 1; i < data.values.length; i++) {
c.lineTo(getXPixel(i), getYPixel(equation(i)));
}
c.stroke();
// Draw the dots
c.fillStyle = '#333';
for (var i = 0; i < data.values.length; i++) {
c.beginPath();
c.arc(getXPixel(i), getYPixel(equation(i)), 4, 0, Math.PI * 2, true);
c.fill();
}
}
var codeText = "";
function parseEquation(input){
// Important that white spaces are removed first
input = input.replace(/\s+/g,""); // remove whitespaces
input = input.replace(/([\-\+])([xy])/g,"$11$2"); // convert -x -y or +x +y to -1x -1y or +1x +1y
// just to make the logic below a little simpler
var newTerm = () => {term = { val : null, scalar : 1, left : left, };} // create a new term
var pushTerm = () => {terms.push(term); term = null;} // push term and null current
// regExp [xy=] gets "x","y", or "="" or [\-\+]??[0-9\.]+ gets +- number with decimal
var reg =/[xy=]|[\-\+]??[0-9\.eE]+/g; // regExp to split the input string into parts
var parts = input.match(reg); // get all the parts of the equation
var terms = []; // an array of all terms parsed
var term = null; // Numbers as constants and variables with scalars are terms
var left = true; // which side of equation a term is
parts.forEach(p=>{
if (p === "x" || p === "y") {
if (term !== null && term.val !== null) { // is the variable defined
pushTerm(); // yes so push to the stack and null
}
if (term === null) { newTerm(); } // do we need a new term?
term.val = p;
} else if( p === "="){ // is it the equals sign
if (!left) { throw new SyntaxError("Unxpected `=` in equation."); }
if (term === null) { throw new SyntaxError("No left hand side of equation."); }// make sure that there is a left side
terms.push(term); // push the last left side term onto the stack
term = null;
left = false; // everything on the right from here on in
} else { // all that is left are numbers (we hope)
if (isNaN(p)){ throw new SyntaxError("Unknown value '"+p+"' in equation"); }//check that there is a number
if (term !== null && (p[0] === "+" || p[0] === "-")){ // check if number is a new term
pushTerm(); // yes so push to the stack and null
}
if(term === null){ newTerm(); } // do we need a new term?
term.scalar *= Number(p); // set the scalar to the new value
}
});
if(term !== null){// there may or may not be a term left to push to the stack
pushTerm();
}
// now simplify the equation getting the scalar for left and right sides . x on left y on right
var scalarX = 0;
var scalarY = 0
var valC = 0; // any constants
terms.forEach(t => {
t.scalar *= !t.left ? -1 : 1; // everything on right is negative
if (t.val === "y") {
scalarY += -t.scalar; // reverse sign
} else if (t.val === "x") {
scalarX += t.scalar;
} else {
valC += t.scalar;
}
})
// now build the code string for the equation to solve for x and return y
var code = "return (" + scalarX + " * x + (" + valC + ")) / "+scalarY +";\n";
codeText = code;
var equation = new Function("x",code); // create the function
return equation;
}
function parseAndPlot(){
var input = eqInput.value;
try{
var equation = parseEquation(input);
plot(equation);
error.textContent ="Plot of "+input+ " as 'function(x){ "+codeText+"}'";
}catch(e){
error.textContent = "Error parsing equation. " + e.message;
}
}
var button = document.getElementById("plot");
var eqInput = document.getElementById("equation-text");
var error = document.getElementById("status");
button.addEventListener("click",parseAndPlot);
parseAndPlot();<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<canvas id="graph" width="200" height="150"></canvas> <br>
Enter a linear equation : <input id="equation-text" value="x2 + 5y = 250" type="text"></input><input id="plot" value="plot" type=button></input><div id="status"></div>
我在线性方程中的解析器中有一些代码，但我想在非线性方程中解析如何在数学中的非线性方程中编写解析器，例如x3 + x4-20x2 = 0和x ^ 100 + x ^ 200 + x ^ 1000 = 0如何查找功率解析器值，请帮助我。