help for epresent (Till Ittermann)

epresent - Presentation of non-linear relationships in regression models with log or logit-link

epresent depvar transformedexposure exposure confounder [if] [pweight] [, options]

Mandatory options
reg Choice of regression type

center Level of exposure to which exp(beta) should be calculated

output Specification whether exp(beta) should be reported for percentiles or values of the exposure)

Voluntary options
nq If output = percentiles: Number of percentiles for which exp(beta) should be calculated; default is 10

tpoints If output = values: Values for which exp(beta) should be calculated

crange Specification of the range around the center level; default is 0.001

plotres Restriction of the plot to a specific xrange

ytitle Title option for the y axis

xtitle Title option for the x axis

xlabel Label option for the x axis

ylabel Label option for the y axis

format Formatting option for the exposure levels

regopt Options for the regression model

title Title option for the graphic

legend Legend option for mlogit

pweights are allowed;see weight.

Description

epresent reports exp(beta) for non-linear associations between a previously transformed or untransformed exposure
(specified in transformedexposure) and an outcome (specified by depvar) on the original scale
of the exposure (specified in exposure). exp(beta)'s are calculated to a reference level of the exposure,
the number of comparing levels is specified in the nq option. To model non-linear relationships between the previously transformed
or untransformed exposure and the outcome the mfp command is used. epresent reports a table including exp(beta)'s and
its confidence intervals for the chosen quantiles of the exposure in comparison to the reference level of the exposure.
Furthermore a graphic of the exp(beta)'s over the full range of the exposure is presented.

Options

Main

reg: Choice of the regression type. Allowed are logistic regression, Poisson regression, Cox regression,
negative binomial regression, Gamma generalized linear model [Option: f(gamma) link(log) eform], and
multinomial logistic regression.

center: Level of the exposure to which exp(beta) should be compared.

output: exp(beta) can be either calculated for percentiles of the exposure or for values of the exposure.

nq: Number of Quantiles of the exposure for which exp(beta) should be calculated in comparison to
the reference level as specified in the center option; default is 10. Should only be specified if output(percentiles).

tpoints: List of values for which exp(beta) should be calculated. No exotic values should be provided here; only values which have
observed values in the range of the value +/- crange*SD. Should only be specified if output(values).

crange: It sometimes happens, that the level of the exposure specified in the center option is not observed in the
dataset. Therefore, a small range around the center point is allowed, which is by default center +/- 0.001*SD(exposure). If this default range
is not sufficient you might specify larger range (e.g. crange(0.01)), which allows a range of center +/- 0.01*SD(exposure). The number
of observations in this range as well as summary statistics of these observations are given as output of epresent. The mean level of
these observations is used as center level.

plotres: Sometimes you don't want to plot exp(beta) for the full range of the exposure. Then you could specify restrictions of the exposure
range by plotres(if exposure < > number).

ytitle xtitle ylabel xlabel: Title and label options for the y- and x-axis as specified in axis options.

format: Formatting option for the exposure levels in the reported table, see format, default is the original format.

regopt: Regression options for the chosen regression type as specified in the respective regression commands. Also options for the
mfp command except the centering option can be used here. Note that glm should only be used with regression models having a log-link.

title: Title for the graphic, see title options

legend: Positioning of the legend in epresent graphics using multinomial logistic regression,
see legend options. For the other regression types the legend is disabled.

Examples

previously untransformed exposure

. sysuse auto

. epresent foreign price price length turn, reg(logistic) center(5079) output(percentiles)

. epresent foreign price price length turn, reg(logistic) center(5079) output(percentiles) plotres(if price<6000) ylabel(0(1)7)

. epresent foreign price price length turn, reg(logistic) center(5079) output(percentiles) nq(20) plotres(if price<6000) ylabel(0(1)7)

. epresent foreign price price length turn, reg(poisson) center(5079) output(values) tpoints(4000(500)7000) crange(.1) regopt(vce(robust)) plotres(if price<6000) ylabel(0(1)7)

previously power-transformed exposure by gdelta

. gdelta pprice = price

. epresent foreign pprice price length turn, reg(poisson) center(5079) output(percentiles) nq(20) regopt(vce(robust)) plotres(if price<6000) ylabel(0(1)8)

If you have any issues with epresent please contact me: till.ittermann@uni-greifswald.de