add option to calculate "n(%)" percentages over a row. Ref #108

[tompollard]

Addresses #108 by adding a row_percent argument. If row_percent = True then the percentage for categorical variables will be calculated over the row (rather than column).

from tableone import TableOne, load_dataset
data = load_dataset('pn2012')

columns = ['Age', 'SysABP', 'Height', 'MechVent', 'ICU', 'death']

# columns containing categorical variables
categorical = ['ICU', 'MechVent']

# set decimal places for age to 0
decimals = {"Age": 0}

# non-normal variables
nonnormal = ['Age']

# optionally, a categorical variable for stratification
groupby = ['death']

t1 = TableOne(data, columns=columns,  categorical=categorical, groupby=groupby,
                        nonnormal=nonnormal, decimals=decimals, row_percent=True)

print(t1.tabulate(tablefmt = "github"))

		Missing	Overall	0	1
n			1000	864	136
Age, median [Q1,Q3]		0	68 [53,79]	66 [53,78]	75 [62,83]
SysABP, mean (SD)		291	114.3 (40.2)	115.4 (38.3)	107.6 (49.4)
Height, mean (SD)		475	170.1 (22.1)	170.3 (23.2)	168.5 (11.3)
MechVent, n (%)	0	0	540 (100.0)	468 (86.7)	72 (13.3)
	1		460 (100.0)	396 (86.1)	64 (13.9)
ICU, n (%)	CCU	0	162 (100.0)	137 (84.6)	25 (15.4)
	CSRU		202 (100.0)	194 (96.0)	8 (4.0)
	MICU		380 (100.0)	318 (83.7)	62 (16.3)
	SICU		256 (100.0)	215 (84.0)	41 (16.0)