Plotly地震地图绘制遇负震级报错：如何过滤负数值？

我用Plotly绘制近期地震数据地图，想根据震级设置点的大小，但数据里有负震级记录，运行代码时报错：

The 'size' property is a number and may be specified as:

• An int or float in the interval [0, inf]
• A tuple, list, or one-dimensional numpy array of the above

我添加了if mag > 0的过滤条件但并未生效，代码如下：

import json
from plotly.graph_objs import Scattergeo, Layout
from plotly import offline
from plotly import colors

# explore the structure of the data
filename = "data/all_month.geojson"
with open(filename) as f:
    all_eq_data = json.load(f)
    
all_eq_dicts = all_eq_data["features"]
title = all_eq_data["metadata"]["title"]

mags, lons, lats, hover_texts = [], [], [], [],
for eq_dict in all_eq_dicts:
    if mag > 0:
        mags.append(eq_dict["properties"]["mag"])
        lons.append(eq_dict["geometry"]["coordinates"] [1])
        lats.append(eq_dict["geometry"]["coordinates"] [0])
        hover_texts.append(eq_dict["properties"]["title"])


# Map the earthquakes
data = [{
    "type": "scattergeo",
    "lon": lons,
    "lat": lats,
    "text": hover_texts,
    "marker": {
        "size": [5*mag for mag in mags],
        "color": mags,
        "colorscale": "Viridis",
        "reversescale": True,
        "colorbar": {"title": "Magnitude"},
    },
}]

my_layout = Layout(title=title)

fig = {"data": data, "layout": my_layout}
offline.plot(fig, filename="global_month_earthquakes_2023.html")

问题原因 #

你写的if mag > 0中的mag变量未提前定义，循环里还没获取当前地震的震级就做判断，导致这个条件完全没起到过滤作用，负震级数据仍被加入列表，最终传给Plotly的size属性包含负值，触发错误。

修正方案 #

先从当前eq_dict中取出震级，再做非负判断，同时处理震级为None的情况（避免类型错误）。修正后的代码：

import json
from plotly.graph_objs import Scattergeo, Layout
from plotly import offline
from plotly import colors

# explore the structure of the data
filename = "data/all_month.geojson"
with open(filename) as f:
    all_eq_data = json.load(f)
    
all_eq_dicts = all_eq_data["features"]
title = all_eq_data["metadata"]["title"]

mags, lons, lats, hover_texts = [], [], [], []
for eq_dict in all_eq_dicts:
    mag = eq_dict["properties"]["mag"]
    # 过滤掉负震级和空值
    if mag is not None and mag > 0:
        mags.append(mag)
        lons.append(eq_dict["geometry"]["coordinates"][1])
        lats.append(eq_dict["geometry"]["coordinates"][0])
        hover_texts.append(eq_dict["properties"]["title"])


# Map the earthquakes
data = [{
    "type": "scattergeo",
    "lon": lons,
    "lat": lats,
    "text": hover_texts,
    "marker": {
        "size": [5*mag for mag in mags],
        "color": mags,
        "colorscale": "Viridis",
        "reversescale": True,
        "colorbar": {"title": "Magnitude"},
    },
}]

my_layout = Layout(title=title)

fig = {"data": data, "layout": my_layout}
offline.plot(fig, filename="global_month_earthquakes_2023.html")

额外优化提示 #

如果不想完全过滤负震级数据，可将负震级转为0（Plotly接受0作为size值），修改判断部分为：

mag = eq_dict["properties"]["mag"]
# 处理空值并将负震级转为0
if mag is None:
    continue
mag = max(mag, 0)
mags.append(mag)
# 后续lons、lats、hover_texts的append代码保留

内容的提问来源于stack exchange，提问作者bavver23