CODEWITHSUNDEEP
pythonpandas
nipy
nipy

Reputation: 5488

Function to capture change between values in different columns

Can someone please help me with a simple function to capture the change between open and Last as per the examples below:

The data:

             Open   High    Low    Last 
Timestamp                                       
2014-03-04  1783.50 1796.00 1783.50 1793.25
2014-03-05  1793.25 1796.50 1790.50 1794.00 
2014-03-06  1798.00 1802.25 1795.00 1797.75 
2014-03-07  1804.75 1805.50 1790.50 1798.75

Its easy enough for me to do a similar function when capturing something like the range between High and Low with:

def daily_range(df):
    return df['High'] - df['Low']

But how do we do a similar function the with Open and Last?

I will use apply on this function to get a new column in my dataframe and desired output is shown below:

           Open   High     Low     Last     Desired output
Timestamp                                       
2014-03-04  1783.50 1796.00 1783.50 1793.25   9.75
2014-03-05  1793.25 1796.50 1790.50 1794.00   0.75
2014-03-06  1798.00 1802.25 1795.00 1797.75  -0.25

Basically if Open is higher than Last I need to do Open - Last and if Last is higher than Open I need to do Last - Open. I could do this with an if in the function but there must be a better way to do this simple task and I would like to find this.

Update:

Sorry if my question was not correctly worded. I did however show desired output with negative values desired output (see above).

On 2014-03-06 below the move was -0.25 but the code given in the answer shows 0.25 not -0.25. Can you help with this?

             Open   Last    desired
Timestamp           
2014-03-04  1783.50 1793.25 9.75
2014-03-05  1793.25 1794.00 0.75
2014-03-06  1798.00 1797.75 0.25

Upvotes: 0

Views: 105

Answers (1)

user2285236
user2285236

Reputation: 

df['desired'] = (df['Open'] - df['Last']).abs()

This gives you the absolute value of the difference (if df['Last'] is greater than df['Open'], it becomes df['Last'] - df['Open'])

Your sample output is, on the other hand, is the result of df['Last'] - df['Open'], without the absolute value.

Upvotes: 3

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