Spatial Survey Data Modeling - Sampling Spatial Units for Agricultural Surveys - page 318

poly(yc, 2)1 16.4636 4.7278 3.482 0.000753 ***

poly(yc, 2)2 -49.6776 4.7026 -10.564 < 2e-16 ***

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Signif. codes: 0 ' *** ' 0.001 ' ** ' 0.01 ' * ' 0.05 ' . ' 0.1 '' 1

Residual standard error: 4.644 on 95 degrees of freedom
Multiple R-squared: 0.8085, Adjusted R-squared: 0.8005
F-statistic: 100.3 on 4 and 95 DF, p-value: < 2.2e-16

> framepop < - cbind(framepop,strataid ¼
+ ceiling(framepop$xc*2)*10+ceiling(framepop$yc*2))
> set.seed(160964)
> str < - strata(framepop,"strataid",size ¼ rep(25,4),
þ method ¼ "srswor")
> str < - getdata(framepop,str)
> dstrsrs < - svydesign(id ¼ ~1,strata ¼ ~strataid,data ¼ str,
þ fpc ¼ ~Prob)
> estrsrs < - svyglm(yobs ~ poly(xc,2)+poly(yc,2),dstrsrs)
> summary(estrsrs)

Call:
svyglm(formula ¼ yobs ~ poly(xc, 2) + poly(yc, 2), dstrsrs)

Survey design:
svydesign(id ¼ ~1, strata ¼ ~strataid, data ¼ str, fpc ¼ ~Prob)

Coefficients:
Estimate Std. Error t value Pr( > |t|)
(Intercept) 91.5548 0.5274 173.611 < 2e-16 ***

poly(xc, 2)1 29.8007 4.8850 6.100 2.47e-08 ***

poly(xc, 2)2 -163.2813 4.8916 -33.380 < 2e-16 ***

poly(yc, 2)1 -1.2067 5.8243 -0.207 0.836

poly(yc, 2)2 -149.8146 5.7154 -26.212 < 2e-16 ***

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Signif. codes: 0 ' *** ' 0.001 ' ** ' 0.01 ' * ' 0.05 ' . ' 0.1 '' 1

(Dispersion parameter for gaussian family taken to be 29.96661)

Number of Fisher Scoring iterations: 2

> regstr < - lm(yobs ~ poly(xc,2)+poly(yc,2), data ¼ str)
> summary(regstr)

Call:
lm(formula ¼ yobs ~ poly(xc, 2) + poly(yc, 2), data ¼ str)