H2O frame functions¶
The following lists all H2O functions that Stata supports. These functions are mainly used in H2O expressions when creating or replacing the contents of the columns in the current H2O frame, or when filtering observations. The functions are organized under the following headings:
Datetime functions¶
day(dt)
Description: the numeric day corresponding to a time column
Domain dt: a time column
Range: an int column with integers 1 to 31 or missing
dow(dt)
Description: the numeric day of the week corresponding to a time column
Domain dt: a time column
Range: an enum column with values Mon, Tue, Wed, Thu, Fri, Sat, Sun,
or missing
hour(dt)
Description: the hour corresponding to a time column
Domain dt: a time column
Range: an int column with integers 0 through 23 or missing
minute(dt)
Description: the minute corresponding to a time column
Domain dt: a time column
Range: an int column with integers 0 through 59 or missing
month(dt)
Description: the numeric month corresponding to a time column
Domain dt: a time column
Range: an int column with integers 1 to 12 or missing
second(dt)
Description: the second corresponding to a time column
Domain dt: a time column
Range: an int column with integers 0 through 59 or missing
week(dt)
Description: the numeric week of the year corresponding to a time column
Note: The first week of a year is the first 7-day period of the
year.
Domain dt: a time column
Range: an int column with integers 1 to 52 or missing
year(dt)
Description: the numeric year corresponding to a time column
Domain dt: a time column
Range: an int column with integers 1 to 9999 or missing
Mathematical functions¶
abs(x)
Description: the absolute value of x
Domain: -infinity to infinity or missing
Range: 0 to infinity or missing
ceil(x)
Description: the unique integer n such that n - 1 < x < n;
or missing if x is missing
Also see floor(x), round(x), and trunc(x).
Domain: -infinity to infinity or missing
Range: integers in -infinity to infinity or missing
exp(x)
Description: the exponential function of e^x
This function is the inverse of log(x).
Domain: -infinity to infinity or missing
Range: 0 to infinity or missing
expm1(x)
Description: e^x - 1
Domain: -infinity to infinity or missing
Range: -1 to infinity or missing
floor(x)
Description: the unique integer n such that n <= x < n + 1;
or missing if x is missing
Also see ceil(x), round(x), and trunc(x).
Domain: -infinity to infinity or missing
Range: integers in -infinity to infinity or missing
log(x)
Description: the natural logarithm
Domain: c(epsdouble) to infinity or missing
Range: -infinity to infinity or missing
log10(x)
Description: the base-10 logarithm of x
Domain: c(epsdouble) to infinity or missing
Range: -infinity to infinity or missing
log1p(x)
Description: the natural logarithm of 1+x
Domain: -1+c(epsdouble) to infinity or missing
Range: -infinity to infinity or missing
log2(x)
Description: the base-2 logarithm of x
Domain: c(epsdouble) to infinity or missing
Range: -infinity to infinity or missing
round(x,digits) or round(x)
Description: x rounded to the number of decimal places specified by digits
If digits is not specified, x will be rounded to an integer.
For rounding, H2O uses the "rounding half to even" mode
(IEC 60559 standard). For example, round(2.5) = 2 and
round(3.5) = 4. Also see ceil(x), floor(x), and trunc(x).
Domain x: -infinity to infinity or missing
Domain digits: integers >= 0
Range: -infinity to infinity or missing
sign(x)
Description: the sign of x: -1 if x < 0, 0 if x = 0, 1 if x > 0, or missing
if x is missing
Domain: -infinity to infinity or missing
Range: -1, 0, 1, or missing
sqrt(x)
Description: the square root of x
Domain: 0 to infinity or missing
Range: 0 to infinity or missing
trunc(x)
Description: the integer obtained by truncating x toward 0 (thus, trunc(5.2) = 5
and trunc(-5.8) = -5), or missing if x is missing
Also see ceil(x), floor(x), and round(x).
Domain: -infinity to infinity or missing
Range: integers in -infinity to infinity or missing
String functions¶
nchar(s)
Description: the number of characters in string s
Domain s: strings
Range: integers >= 0
tolower(s)
Description: lowercase characters in string s
Domain s: strings
Range: strings with lowercase characters
lstrip(s) or lstrip(s,prefix)
Description: s without leading characters
Note: The prefix argument specifies that the string prefix be
removed from the string if it is found at the beginning of the
string.
Domain s: strings
Domain prefix: strings
Range: strings without leading characters
rstrip(s) or rstrip(s,suffix)
Description: s without trailing characters
Note: The suffix argument specifies that the string suffix be
removed from the string if it is found at the end of the string.
Domain s: strings
Domain suffix: strings
Range: strings without trailing characters
toupper(s)
Description: uppercase characters in string s
Domain s: strings
Range: strings with uppercase characters
substring(s,n1,n2)
Description: the substring of s, starting at n1, for a length of n2
If n1 is greater than the length of the string, an empty string is
returned; if n2 = . (missing), the remaining portion of the string
is returned.
Domain s: strings
Domain n1: integers >= 1
Domain n2: integers >= 1
Range: strings
Trigonometric functions¶
acos(x)
Description: the radian value of the arccosine of x
Domain: -1 to 1 or missing
Range: 0 to pi or missing
acosh(x)
Description: the inverse hyperbolic cosine of x,
acosh(x) = ln{x+sqrt(x*x - 1)}
Domain: 1 to infinity or missing
Range: 0 to infinity or missing
asin(x)
Description: the radian value of the arcsine of x
Domain: -1 to 1 or missing
Range: -pi/2 to pi/2 or missing
asinh(x)
Description: the inverse hyperbolic sine of x,
asinh(x) = ln{x+sqrt(x*x + 1)}
Domain: -infinity to infinity or missing
Range: -infinity to infinity or missing
atan(x)
Description: the radian value of the arctangent of x
Domain: -infinity to infinity or missing
Range: -pi/2 to pi/2 or missing
atanh(x)
Description: the inverse hyperbolic tangent of x,
atanh(x) = (1/2){ln(1+x) - ln(1-x)}
Domain: -1 to 1 or missing
Range: -infinity to infinity or missing
cos(x)
Description: the cosine of x, where x is in radians
Domain: -infinity to infinity or missing
Range: -1 to 1 or missing
cosh(x)
Description: the hyperbolic cosine of x,
cosh(x) = {exp(x) + exp(-x)}/2
Domain: -infinity to infinity or missing
Range: 1 to infinity or missing
sin(x)
Description: the sine of x, where x is in radians
Domain: -infinity to infinity or missing
Range: -1 to 1 or missing
sinh(x)
Description: the hyperbolic sine of x,
sinh(x) = {exp(x) - exp(-x)}/2
Domain: -infinity to infinity or missing
Range: -infinity to infinity or missing
tan(x)
Description: the tangent of x, where x is in radians
Domain: -infinity to infinity or missing
Range: -infinity to infinity or missing
tanh(x)
Description: the hyperbolic tangent of x,
tanh(x) = {exp(x) - exp(-x)}/{exp(x) + exp(-x)}
Domain: -infinity to infinity or missing
Range: -1 to 1 or missing