如何比较两个数据框中的坐标？

Question

I have two dataframes

df1

x1	y1	x2	y2	label
0	0	1240	1755	label1
0	0	1240	2	label2

df2

x1	y1	x2	y2	text
992.0	943.0	1166.0	974.0	tex1
1110.0	864.0	1166.0	890.0	text2

Based on a condition like the following:

if df1['x1'] >= df2['x1'] or df1['y1'] >= df2['y1']:
   # I want to add a new column 'text' in df1 with the text from df2.
   df1['text'] = df2['text']

What's more, it is possible in df2 to have more than one row that makes the above-mentioned condition True , so I will need to add another if statement for df2 to get the best match.

My problem here is not the conditions but how am I supposed to approach the interaction between both data frames. Any help, or advice would be appreciated.

Answer 1

If you want to iterate from df1 through every row of df2 and return a match you can do it with the .apply() function in df1 and use the df2 as lookup table.

NOTE: In the above example I return the first match (by using the .iloc[0] ) not all the matches.

Create two dummy dataframes

import pandas as pd

df1 = pd.DataFrame({'x1': [1, 2, 3], 'y1': [1, 5, 6]})
df2 = pd.DataFrame({'x1': [11, 1, 13], 'y1': [3, 52, 26], 'text': ['text1', 'text2', 'text3']})

Create a lookup function

def apply_condition(row, df):
    condition  = ((row['x1'] >= df['x1']) | (row['y1'] >= df['y1']))
    return df[condition]['text'].iloc[0] # ATTENTION: Only the first match return

Create new column and print results

df1['text'] = df1.apply(lambda row: apply_condition(row, df2), axis=1)
df1.head()

Result: