在 Python 中使用 Matplotlib 绘制抛物线图
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Graphing a Parabola using Matplotlib in Python
提问by kman29
I am trying to graph a simple parabola in matplotliband I am confused as to how I am supposed to plot points on the parabola. So far, this is what I have:
我正在尝试绘制一个简单的抛物线matplotlib，但我对如何在抛物线上绘制点感到困惑。到目前为止，这就是我所拥有的：
import matplotlib.pyplot as plt
a=[]
b=[]
y=0
x=-50
while x in range(-50,50,1):
y=x^2+2*x+2
a=[x]
b=[y]
fig= plt.figure()
axes=fig.add_subplot(111)
axes.plot(a,b)
plt.show()
x= x+1
回答by cel
This should do:
这应该做：
import matplotlib.pyplot as plt
import numpy as np
# create 1000 equally spaced points between -10 and 10
x = np.linspace(-10, 10, 1000)
# calculate the y value for each element of the x vector
y = x**2 + 2*x + 2
fig, ax = plt.subplots()
ax.plot(x, y)
回答by tom10
This is your approach with as few changes as possible to make it work (because it's clear that you're a beginner and this is a learning exercise). The changes I made were:
这是您的方法，只需进行尽可能少的更改即可使其发挥作用（因为很明显您是初学者，这是一项学习练习）。我所做的改变是：
Moved the
plt.figure, and other plotting statements out of the loop. The loop now gives you the data to plot, and then you plot it once the loop is finished.Changed
x^2tox**2.Changed
whiletoforin your main loop control statement.Commented out a few lines that weren't doing anything. They all had the same source of error (or non-utility, really): in the for loop,
xis set in the loop control line and thenyis calculated directly, so you don't need to give them initial values or incrementx, though you would have had to do these steps for a while loop.
将
plt.figure, 和其他绘图语句移出循环。循环现在为您提供要绘制的数据，然后在循环完成后绘制它。改
x^2到x**2。在主循环控制语句中更改
while为for。注释掉几行没有做任何事情。它们都有相同的错误来源（或非实用程序，真的）：在 for 循环中，
x在循环控制行中设置，然后y直接计算，因此您不需要给它们初始值或 incrementx，但是您将不得不在一段时间循环中执行这些步骤。
Here the code:
这里的代码：
import matplotlib.pyplot as plt
a=[]
b=[]
# y=0
# x=-50
for x in range(-50,50,1):
y=x**2+2*x+2
a.append(x)
b.append(y)
#x= x+1
fig= plt.figure()
axes=fig.add_subplot(111)
axes.plot(a,b)
plt.show()
回答by heykay47
Adjust your third to last line to:
将倒数第三行调整为：
axes.plot(a,b, 'r-^')
Adding the 'r-^' will add red triangular points to the graph. Alternatively, you can use 'b-o'.
添加“ r-^”将向图形添加红色三角形点。或者，您可以使用“ b-o”。
Note:You should include the quotes.
注意：您应该包括引号。
For different colors you can use 'b' - blue; 'g' - green; 'r' - red; 'c' - cyan; 'm' - magenta; 'y' - yellow; 'k' - black; 'w' - white
对于不同的颜色，您可以使用 'b' - 蓝色；'g' - 绿色；'r' - 红色；'c' - 青色；'m' - 洋红色；'y' - 黄色；'k' - 黑色；'w' - 白色
The - in the 'r-^' or 'b-o' will create the line joining the triangles or circles respectively. That is, without the dash, you will end up with a scatter plot.
' r-^' 或 ' b-o' 中的 - 将分别创建连接三角形或圆形的线。也就是说，如果没有破折号，您将得到一个散点图。
Alternatively, there is command ....scatter(x,y)which would be equivalent to 'r ^' and 'b o'
或者，有命令 ....scatter(x,y)相当于 ' r ^' 和 ' b o'
