对熊猫dataframe的特殊问题添加系列。

I am facing a peculiar issue. I have 2 dataframes, x with 180k rows, y with 700 rows. I am creating another series z by looking up a column from x into y and getting a third column as series. But when I add this series to x, the values change completely. Given below are the two count distributions. Any idea why this could be happening?I am facing a peculiar issue. I have 2 datafram