我正在使用D3和Python创建一些绘图。使用Python,我能够做到轴相等,如图1所示:
我想在使用D3的SVG中实现相同的目的。请参考图2,轴不相等:
我正在使用的轴刻度如下:
var xScale = d3.scaleLinear()
.range([0, width])
.domain([minX, maxX]);
var yScale = d3.scaleLinear()
.range([height, 0])
.domain([minY, maxY]);
var xAxis = d3.axisBottom(xScale).ticks(5),
yAxis = d3.axisLeft(yScale).ticks(5);
谁能告诉我如何使轴与D3相等?
简短的回答:不,D3中没有“轴相等”。D3级别很低,它只是方法的集合,因此您几乎必须手工完成所有工作...
好消息是,您解决问题所需的就是一些数学运算来计算新范围。
As an introduction, since this is a d3.js tagged question, "axis equal" is a term used in some programs like Matlab, which...
Use the same length for the data units along each axis.
It can be better explained visually. Have a look at this image, with different domains and ranges (source):
After this brief introduction, let's go back to your problem. Suppose this simple code, generating two axes:
const minX = 0,
minY = 0,
maxX = 120,
maxY = 50,
width = 500,
height = 300,
paddings = [10, 10, 20, 30];
const xScale = d3.scaleLinear()
.range([paddings[3], width - paddings[1]])
.domain([minX, maxX]);
const yScale = d3.scaleLinear()
.range([height - paddings[2], paddings[0]])
.domain([minY, maxY]);
const svg = d3.select("svg")
.attr("width", width)
.attr("height", height);
svg.append("g")
.attr("transform", `translate(0,${height - paddings[2]})`)
.call(d3.axisBottom(xScale).tickSizeInner(-height + paddings[2] + paddings[0]));
svg.append("g")
.attr("transform", `translate(${paddings[3]},0)`)
.call(d3.axisLeft(yScale).tickValues(xScale.ticks()).tickSizeInner(-width + paddings[3] + paddings[1]));
svg {
border: 2px solid tan;
}
line {
stroke-dasharray: 2, 2;
stroke: gray;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/5.7.0/d3.min.js"></script>
<svg></svg>
As we can clearly see, the units are not equally spaced. We can do two things for creating axes with equally spaced units: 1. Change the domains; 2. Change the ranges.
According to your comment, changing the domains is not an option. So, let's change the ranges instead.
我们所需要的只是计算每个用户空间的单位数,并使用其中最大的一个(x或y)来更改相反刻度的范围。
例如,给定上面片段的比例:
const xStep = Math.abs((xScale.domain()[1] - xScale.domain()[0]) / (xScale.range()[1] - xScale.range()[0]));
const yStep = Math.abs((yScale.domain()[1] - yScale.domain()[0]) / (yScale.range()[1] - yScale.range()[0]));
xStep
大于yStep
,向我们显示x轴每像素具有更多单位。因此,我们将更改y轴范围:
yScale.range([yScale.range()[0], yScale.range()[0] - (yScale.domain()[1] - yScale.domain()[0]) / xStep]);
这是演示:
const minX = 0,
minY = 0,
maxX = 120,
maxY = 50,
width = 500,
height = 300,
paddings = [10, 10, 20, 30];
const xScale = d3.scaleLinear()
.range([paddings[3], width - paddings[1]])
.domain([minX, maxX]);
const yScale = d3.scaleLinear()
.range([height - paddings[2], paddings[0]])
.domain([minY, maxY]);
const xStep = Math.abs((xScale.domain()[1] - xScale.domain()[0]) / (xScale.range()[1] - xScale.range()[0]));
const yStep = Math.abs((yScale.domain()[1] - yScale.domain()[0]) / (yScale.range()[1] - yScale.range()[0]));
yScale.range([yScale.range()[0], yScale.range()[0] - (yScale.domain()[1] - yScale.domain()[0]) / xStep]);
const svg = d3.select("svg")
.attr("width", width)
.attr("height", height);
svg.append("g")
.attr("transform", `translate(0,${height - paddings[2]})`)
.call(d3.axisBottom(xScale).tickSizeInner(-height + paddings[2] + yScale.range()[1]));
svg.append("g")
.attr("transform", `translate(${paddings[3]},0)`)
.call(d3.axisLeft(yScale).tickValues(yScale.ticks().filter(function(d){return !(+d%10)})).tickSizeInner(-width + paddings[3] + paddings[1]));
svg {
border: 2px solid tan;
}
line {
stroke-dasharray: 2, 2;
stroke: gray;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/5.7.0/d3.min.js"></script>
<svg></svg>
如您所见,使用网格线时,单位之间的距离现在相等。
最后,请记住,以编程方式确定将要更改的比例尺,重新调整正确的范围(例如,您的比例尺从底部到顶部),将轴居中等完全是不同的问题。
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