如何使用自定义轴绘制图形

Question

我为此问道歉，我相信这是一项简单的任务，但我不知道该怎么做。

假设我有一个公式y = (exp(-x) + x^2)/sqrt(pi(x)，我想将其绘制为y与x^2。

如何做到这一点？

Answer 1

像这样：

 X = 0:0.1:5;   %// Get the x values
 x = X.^2;      %// Square them
 %// Your formula had errors, I fixed them but I could have misinterpreted here, please check
 y = (exp(-x) + x.^2)./sqrt(pi*x);   %// Calculate y at intervals based on the squared x. This is still y = f(x), I'm just calculating it at the points at which I want to plot it.

 plot(x,y) %//Plot against the square X.

在这一点上，这与正常绘制它没有什么不同。你想要的是使得标记在X.^2的值上升。这不会改变y值也不会扭曲函数，它只会改变它的视觉效果。与绘制对数刻度相似：

set(gca, 'XTick', X.^2)  %//Set the tickmarks to be squared

第二种方法给你一个类似的情节

修改

实际上我认为你是这样要求的：

x = 0:0.1:5;
y = x.^2;   %// Put your function in here, I'm using a simple quadratic for illustrative purposes. 
plot(x.^2,y) %//Plot against the square X. Now your y values a f(x^2) which is wrong, but we'll fix that later
set(gca, 'XTick', (0:0.5:5).^2)  %//Set the tickmarks to be a nonlinear intervals
set(gca, 'XTickLabel', 0:0.5:5)  %//Cahnge the labels to be the original x values, now accroding to the plot y = f(x) again but has the shape of f(x^2)

所以这里我正在绘制一个简单的二次曲线，但是如果我将其绘制成平方x，它应该变成线性的。但是我仍然想要读出y = x ^ 2的图形，而不是y = x，我只是希望它看起来像y = x。因此，如果我在该图上读取x值为4的y值，我将得到16，这仍然是正确的原始y值。

Answer 2

这是我的答案：它与Dan的相似，但根本不同。您可以将y的值计算为x的函数，但将其绘制为x^2的函数，这是OP所要求的，如果我的理解是正确的：

x = 0:0.1:5;   %// Get the x values
x_squared = x.^2;      %// Square them
%// Your formula had errors, I fixed them but I could have misinterpreted here, please check
y = (exp(-x) + x.^2)./sqrt(pi*x);   %// Calculate y based on x, not the square of x

plot(x_squared,y) %//Plot against the square of x

正如丹所提到的，您可以随时更改标记：

x_ticks = (0:0.5:5).^2; % coarser vector to avoid excessive number of ticks
set(gca, 'XTick', x_ticks)  %//Set the tickmarks to be squared