Reputation: 487
So I am having dataframe which looks like this
v1 v2
day1 x x
day2 x x
day3 x x
day4 x x
day5 x x
What I need is to add new column v3 which will be the difference "today's v1 - yesterday's v2"
I've tried df[v3] = df[v1][1:] - df[v2][:-1]
But it looks like python is somehow mapping rows by timestamp and I am receiving "today's v1 - today's v2" as result except for first and last rows which are NaN.
Upvotes: 1
Views: 43
Reputation: 25269
IIUC, as your days monotonic increasing, you may subtract v1
by v2.shift()
df['v3'] = df.v1 - df.v2.shift()
Upvotes: 2