如何解决Matplotlib 以一种非常奇怪的方式绘制图形
尝试绘制一天中的紫外线指数。数据来自一个 api,经过一些处理后,它为我提供了一个不错的列表中的数据。不过剧情实在是太恶心了。 Link to graph。 Y轴的值被重复抛来抛去,所以出现了多个0,多个0的两边都是正数,解释的噩梦。提前致谢
代码:
import requests
import re
from matplotlib import pyplot as plt
import numpy as np
# Get weather information
response = requests.get("https://api.openweathermap.org/data/2.5/onecall?lat=55.583328&lon=13.0&lang=se&exclude=minutely,daily,alerts&units=metric&appid=0f0212703cfecb4699dfc2c7edde950a")
# Save weather information to file
with open("weather.csv",'w') as file:
file.write(response.text)
# Opens the file and gets all the values of "uv-index"
with open("Weather.csv",'r') as text:
pattern = 'uvi":(.*?),'
Line = text.read()
substring = np.array(re.findall(pattern,Line))
# Creates an x-axis as a list with the same size as y-axis
# If they're not the same size,error is given:
# ValueError: x and y must have same first dimension,but have shapes (12,) and (49,)
x_axis = []
for i in range(len(substring)):
x_axis.append(i)
x_axis = np.array(x_axis)
# Determines size and plots graph
fig,ax = plt.subplots(figsize=(10,6))
ax.plot(x_axis,substring)
# Creates labels
plt.title("UV-Index today")
plt.xlabel("Time")
plt.ylabel("UV-Index")
# Saves the plot as image and shows it on screen
plt.savefig("UV-Index" + ".png")
plt.show()
解决方法
这解决了所有问题,代码一目了然,但请询问您是否对任何事情感到困惑:
import requests
import re
from matplotlib import pyplot as plt
import numpy as np
import json
response = requests.get("https://api.openweathermap.org/data/2.5/onecall?lat=55.583328&lon=13.0&lang=se&exclude=minutely,daily,alerts&units=metric&appid=0f0212703cfecb4699dfc2c7edde950a")
with open("weather.txt",'w') as file:
file.write(response.text)
# this converts the JSON as a string to JSON as a dictionary
dict1 = json.loads(response.text)
y_axis = []
for entry in dict1['hourly']:
y_axis.append(entry['uvi'])
y_axis = np.array(y_axis)
x_axis = np.array(range(len(x_axis)))
fig,ax = plt.subplots(figsize=(10,6))
ax.plot(x_axis,y_axis)
plt.title("UV-Index today")
plt.xlabel("Time (Hours)")
plt.ylabel("UV-Index")
plt.savefig("UV-Index" + ".png")
plt.show()
(另外,检查您的 weather.csv
文件;它不应该是 csv
格式,因为它是 json 数据,而不是表数据。)
您的 substring
是一个字符串列表。 Matplotlib 将字符串视为离散值(因此“0”和“0.01”以及“0”和“1000”之间的距离没有差异;并且它们之间没有顺序,因此“1000”可能看起来低于“0”)。
在绘图前将您的 substring
转换为浮动:
substring = list(map(float,substring))
或者,因为您的子字符串是一个 numpy 数组:
substring = substring.astype('float')
,
如前所述,您的 Y 数据不是数字类型。
这绝对是一种解析 json 响应的新方法。试试这个:
import json
s = json.loads(response.text)
df = pd.json_normalize(s['hourly'])
df['dt'] = pd.to_datetime(df['dt'],unit='s')
df.plot(x="dt",y='uvi')
# Creates labels
plt.title("UV-Index today")
plt.xlabel("Time")
plt.ylabel("UV-Index")
plt.show()
根据要求,完整示例。不确定为什么将结果保存到文本文件中,但它是 json
文件而不是 csv
文件。
import requests
from matplotlib import pyplot as plt
import json
import pandas as pd
import numpy as np
# Get weather information
response = requests.get("https://api.openweathermap.org/data/2.5/onecall?lat=55.583328&lon=13.0&lang=se&exclude=minutely,alerts&units=metric&appid=0f0212703cfecb4699dfc2c7edde950a")
# Save weather information to file
with open("weather.json",'w') as file:
file.write(response.text)
# Evaluate JSON string to JSON object
s = json.loads(response.text)
# Create DataFrame with hourly data
df = pd.json_normalize(s['hourly'])
# Convert time stamps to actual datetime values
df['dt'] = pd.to_datetime(df['dt'],unit='s')
# Determines size and plots graph
df.plot(x="dt",y='uvi',figsize=(10,6))
# Creates labels
plt.title("UV-Index today")
plt.xlabel("Time")
plt.ylabel("UV-Index")
# Saves the plot as image and shows it on screen
plt.savefig("UV-Index" + ".png")
plt.show()
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