Regression Thomas J. Leeper Department of Political Science and - - PowerPoint PPT Presentation

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Regression Thomas J. Leeper Department of Political Science and - - PowerPoint PPT Presentation

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Models Objects and Output Interactions Regression Thomas J. Leeper Department of Political Science and Government Aarhus University November 14, 2013 Models Objects and Output Interactions Models Objects and Output Interactions Models

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Models Objects and Output Interactions

Regression

Thomas J. Leeper

Department of Political Science and Government Aarhus University

November 14, 2013

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Models Objects and Output Interactions

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Models Objects and Output Interactions

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Models

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Objects and Output

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Interactions

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Models Objects and Output Interactions

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Models

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Objects and Output

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Interactions

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Models Objects and Output Interactions

Model Formulæ

Express relationships as a formula Typically: y x1 + x2 Interactions: y x1 * x2 y x1 + x2 + x1:x2 Formula is an object

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Models Objects and Output Interactions

Try on your own

Understand formulae: “Model Formulae”

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Models Objects and Output Interactions

Questions so far?

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Models Objects and Output Interactions

Running a regression

We already ran regressions earlier Let’s understand what we did

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Models Objects and Output Interactions

The regression from earlier

lm3_1 <- lm(thresh~threat + fragdum, data = cis) lm3_2 <- lm(thresh~threat + fragdum, data=cis[cis$oursmpl==1,]) lm3_3 <- lm(thresh~threat13 + fragdum, data=cis[cis$oursmpl==1,]) lm3_4 <- lm(thresh~stthroct2 + fragdum, data=cis[cis$oursmpl==1,])

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Models Objects and Output Interactions

Running a regression

The linear regression function is lm Specify a formula and a place to look for data The result is an object of class “lm”

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Models Objects and Output Interactions

The regression from earlier

lm3_1 <- lm(thresh~threat + fragdum, data = cis) lm3_2 <- lm(thresh~threat + fragdum, data=cis[cis$oursmpl==1,]) lm3_3 <- lm(thresh~threat13 + fragdum, data=cis[cis$oursmpl==1,]) lm3_4 <- lm(thresh~stthroct2 + fragdum, data=cis[cis$oursmpl==1,])

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Models Objects and Output Interactions

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Models

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Objects and Output

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Interactions

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Models Objects and Output Interactions

Printing

When we run a regression, we get some default

  • utput:

lm(thresh~threat + fragdum, data = cis)

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Models Objects and Output Interactions

Printing

When we run a regression, we get some default

  • utput:

lm(thresh~threat + fragdum, data = cis) This doesn’t print if we store the results: lm3_1 <- lm(thresh~threat + fragdum, data = cis)

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Models Objects and Output Interactions

Printing

When we run a regression, we get some default

  • utput:

lm(thresh~threat + fragdum, data = cis) This doesn’t print if we store the results: lm3_1 <- lm(thresh~threat + fragdum, data = cis) But we can see the results again, once stored, by simply calling: lm3_1

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Models Objects and Output Interactions

Structure and summary

Structure: str(lm3_1) Names: names(lm3_1) Summary: summary(lm3_1)

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Coefficients

Coefficients: coef(lm3_1) lm3_1$coef coef(summary(lm3_1)) summary(lm3_1)$coef

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Models Objects and Output Interactions

Try on your own

Understand OLS coefficient plotting: “OLS Coefficients”

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Models Objects and Output Interactions

Questions so far?

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Fitted values and residuals

lm3_1$fitted lm3_1$resduals predict(lm3_1)

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Models Objects and Output Interactions

Try on your own

Understand model fit: “OLS Diagnostic Plots” “Regression fit”

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Models Objects and Output Interactions

Questions so far?

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Writing Output to Word

Writing a CSV Using the rtf package: install.packages("rtf") library(rtf)

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Models Objects and Output Interactions

Try on your own

Output results to Word: “Word output”

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Questions so far?

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Models Objects and Output Interactions

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Models

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Objects and Output

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Interactions

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Let’s work together

“Binary interactions” “Continuous interactions”

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