NameError: name 'ema' is not defined

[akitxu]

Dear all. When executing the function that calculates the MACD, it gives me the following error show on the titlle.

`import pandas as pd
import yfinance as yf

def macd(data, period_long=26, period_short=12, period_signal=9, column='Close'):
remove_cols = []
if not 'ema' + str(period_long) in data.columns:
data = ema(data, period_long)
remove_cols.append('ema' + str(period_long))

if not 'ema' + str(period_short) in data.columns:
    data = ema(data, period_short)
    remove_cols.append('ema' + str(period_short))

data['macd_val'] = data['ema' + str(period_short)] - data['ema' + str(period_long)]
data['macd_signal_line'] = data['macd_val'].ewm(ignore_na=False, min_periods=0, com=period_signal, adjust=True).mean()

data = data.drop(remove_cols, axis=1)
    
return data

data = yf.download('AAPL', start= '2016-1-4', end = '2021-12-30')

data = macd(data, period_long=26, period_short=12, period_signal=9, column='Close')
data

NameError Traceback (most recent call last)
/tmp/ipykernel_12947/116451859.py in
21 data = yf.download('AAPL', start= '2016-1-4', end = '2021-12-30')
22
---> 23 data = macd(data, period_long=26, period_short=12, period_signal=9, column='Close')
24 data

/tmp/ipykernel_12947/116451859.py in macd(data, period_long, period_short, period_signal, column)
5 remove_cols = []
6 if not 'ema' + str(period_long) in data.columns:
----> 7 data = ema(data, period_long)
8 remove_cols.append('ema' + str(period_long))
9

NameError: name 'ema' is not defined`

I don't understand this error. I will appreciate clarification

I don't understand this error.