Join points with a parabolic interpolator, for Chris Henrick.
See the sinusoidal version.
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Parabolic interpolation
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| license: mit |
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| <!DOCTYPE html> | |
| <head> | |
| <meta charset="utf-8"> | |
| <script src="https://d3js.org/d3.v4.min.js"></script> | |
| <style> | |
| body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; } | |
| </style> | |
| </head> | |
| <body> | |
| <script> | |
| var svg = d3.select("body").append("svg") | |
| .attr("width", width = 960) | |
| .attr("height", height = 500) | |
| var steps = 400; | |
| var parset = d3.timeParse('%m/%d/%y %H:%M'); | |
| var data = d3.csvParse(`Date_Time,Event,Speed | |
| 3/31/17 0:24,flood,1.59 | |
| 3/31/17 3:42,slack,0 | |
| 3/31/17 7:12,ebb,-1.86 | |
| 3/31/17 10:30,slack,0 | |
| 3/31/17 13:12,flood,1.43 | |
| 3/31/17 17:00,slack,0 | |
| 3/31/17 20:00,ebb,-1.45 | |
| 3/31/17 22:42,slack,0 | |
| 4/1/17 1:12,flood,1.48 | |
| 4/1/17 4:24,slack,0 | |
| 4/1/17 8:06,ebb,-1.74 | |
| 4/1/17 11:30,slack,0 | |
| 4/1/17 14:06,flood,1.23 | |
| 4/1/17 18:06,slack,0 | |
| 4/1/17 21:00,ebb,-1.25 | |
| 4/1/17 23:36,slack,0`) | |
| .map(d => { | |
| d.time = +parset(d.Date_Time); | |
| d.speed = +d.Speed; | |
| return d; | |
| }); | |
| var x = d3.scaleLinear() | |
| .domain(d3.extent(data.map(d => d.time))) | |
| .range([0,width]); | |
| var y = d3.scaleLinear() | |
| .domain(d3.extent(data.map(d => d.speed))) | |
| .range([height,0]); | |
| function inter(t){ | |
| var prev = d3.bisectLeft(data.map(d => d.time), t)-1, | |
| r = 0; | |
| if (!data[prev]) return 0; | |
| var alpha = (t - data[prev].time) / (data[prev+1].time - data[prev].time); | |
| if (data[prev].Event == 'slack') | |
| alpha = 1 - (1 - alpha) * (1 - alpha); | |
| else | |
| alpha = alpha * alpha; | |
| r = d3.interpolateNumber(data[prev].speed, data[prev+1].speed)(alpha); | |
| return r; | |
| } | |
| var line = d3.line().x(x).y(u => y(inter(u))); | |
| svg.append('path') | |
| .attr('fill', 'none') | |
| .attr('stroke', 'lightblue') | |
| .attr('d', line(d3.range( | |
| ...x.domain(), | |
| (x.domain()[1] - x.domain()[0]) / steps | |
| ))) | |
| svg.selectAll('circle') | |
| .data(data) | |
| .enter() | |
| .append('circle') | |
| .attr('r', 4) | |
| .attr('cx', d => x(d.time)) | |
| .attr('cy', d => y(d.speed)) | |
| </script> | |
| </body> |
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