Copyright 2016 Allen B. Downey
MIT License: https://opensource.org/licenses/MIT
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from __future__ import print_function, division
import nsfg
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preg = nsfg.ReadFemPreg()
preg.head()
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Print the column names.
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preg.columns
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Select a single column name.
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preg.columns[1]
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Select a column and check what type it is.
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pregordr = preg['pregordr']
type(pregordr)
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Print a column.
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pregordr
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Select a single element from a column.
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pregordr[0]
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Select a slice from a column.
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pregordr[2:5]
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Select a column using dot notation.
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pregordr = preg.pregordr
Count the number of times each value occurs.
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preg.outcome.value_counts().sort_index()
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Check the values of another variable.
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preg.birthwgt_lb.value_counts().sort_index()
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Make a dictionary that maps from each respondent's caseid to a list of indices into the pregnancy DataFrame. Use it to select the pregnancy outcomes for a single respondent.
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caseid = 10229
preg_map = nsfg.MakePregMap(preg)
indices = preg_map[caseid]
preg.outcome[indices].values
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Select the birthord column, print the value counts, and compare to results published in the codebook
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# Solution
preg.birthord.value_counts().sort_index()
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We can also use isnull to count the number of nans.
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preg.birthord.isnull().sum()
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Select the prglngth column, print the value counts, and compare to results published in the codebook
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# Solution
preg.prglngth.value_counts().sort_index()
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To compute the mean of a column, you can invoke the mean method on a Series. For example, here is the mean birthweight in pounds:
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preg.totalwgt_lb.mean()
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Create a new column named totalwgt_kg that contains birth weight in kilograms. Compute its mean. Remember that when you create a new column, you have to use dictionary syntax, not dot notation.
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# Solution
preg['totalwgt_kg'] = preg.totalwgt_lb / 2.2
preg.totalwgt_kg.mean()
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nsfg.py also provides ReadFemResp, which reads the female respondents file and returns a DataFrame:
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resp = nsfg.ReadFemResp()
DataFrame provides a method head that displays the first five rows:
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resp.head()
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Select the age_r column from resp and print the value counts. How old are the youngest and oldest respondents?
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# Solution
resp.age_r.value_counts().sort_index()
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We can use the caseid to match up rows from resp and preg. For example, we can select the row from resp for caseid 2298 like this:
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resp[resp.caseid==2298]
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And we can get the corresponding rows from preg like this:
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preg[preg.caseid==2298]
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How old is the respondent with caseid 1?
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# Solution
resp[resp.caseid==1].age_r
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What are the pregnancy lengths for the respondent with caseid 2298?
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# Solution
preg[preg.caseid==2298].prglngth
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What was the birthweight of the first baby born to the respondent with caseid 5012?
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# Solution
preg[preg.caseid==5012].birthwgt_lb
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