R version 2.12.1 (2010-12-16) Copyright (C) 2010 The R Foundation for Statistical Computing ISBN 3-900051-07-0 Platform: x86_64-redhat-linux-gnu (64-bit) R is free software and comes with ABSOLUTELY NO WARRANTY. You are welcome to redistribute it under certain conditions. Type 'license()' or 'licence()' for distribution details. R is a collaborative project with many contributors. Type 'contributors()' for more information and 'citation()' on how to cite R or R packages in publications. Type 'demo()' for some demos, 'help()' for on-line help, or 'help.start()' for an HTML browser interface to help. Type 'q()' to quit R. > x <- array(list(1235,127,13,1080,115,12,845,127,7,1522,150,9,1047,156,6,1979,182,11,1822,156,12,1253,132,10,1297,137,9,946,113,9,1713,137,15,1024,117,11,1147,137,8,1092,153,6,1152,117,13,1336,126,10,2131,170,14,1550,182,8,1884,162,11,2041,184,10,845,143,6,1483,159,9,1055,108,14,1545,175,8,729,108,6,1792,179,9,1175,111,15,1593,187,8,785,111,7,744,115,7,1356,194,5,1262,168,7),dim=c(3,32),dimnames=list(c('Veilingprijs','Ouderdom','Aanbieders'),1:32)) > y <- array(NA,dim=c(3,32),dimnames=list(c('Veilingprijs','Ouderdom','Aanbieders'),1:32)) > for (i in 1:dim(x)[1]) + { + for (j in 1:dim(x)[2]) + { + y[i,j] <- as.numeric(x[i,j]) + } + } > par3 = 'No Linear Trend' > par2 = 'Do not include Seasonal Dummies' > par1 = '1' > #'GNU S' R Code compiled by R2WASP v. 1.0.44 () > #Author: Prof. Dr. P. Wessa > #To cite this work: AUTHOR(S), (YEAR), YOUR SOFTWARE TITLE (vNUMBER) in Free Statistics Software (v$_version), Office for Research Development and Education, URL http://www.wessa.net/rwasp_YOURPAGE.wasp/ > #Source of accompanying publication: Office for Research, Development, and Education > #Technical description: Write here your technical program description (don't use hard returns!) > library(lattice) > library(lmtest) Loading required package: zoo > n25 <- 25 #minimum number of obs. for Goldfeld-Quandt test > par1 <- as.numeric(par1) > x <- t(y) > k <- length(x[1,]) > n <- length(x[,1]) > x1 <- cbind(x[,par1], x[,1:k!=par1]) > mycolnames <- c(colnames(x)[par1], colnames(x)[1:k!=par1]) > colnames(x1) <- mycolnames #colnames(x)[par1] > x <- x1 > if (par3 == 'First Differences'){ + x2 <- array(0, dim=c(n-1,k), dimnames=list(1:(n-1), paste('(1-B)',colnames(x),sep=''))) + for (i in 1:n-1) { + for (j in 1:k) { + x2[i,j] <- x[i+1,j] - x[i,j] + } + } + x <- x2 + } > if (par2 == 'Include Monthly Dummies'){ + x2 <- array(0, dim=c(n,11), dimnames=list(1:n, paste('M', seq(1:11), sep =''))) + for (i in 1:11){ + x2[seq(i,n,12),i] <- 1 + } + x <- cbind(x, x2) + } > if (par2 == 'Include Quarterly Dummies'){ + x2 <- array(0, dim=c(n,3), dimnames=list(1:n, paste('Q', seq(1:3), sep =''))) + for (i in 1:3){ + x2[seq(i,n,4),i] <- 1 + } + x <- cbind(x, x2) + } > k <- length(x[1,]) > if (par3 == 'Linear Trend'){ + x <- cbind(x, c(1:n)) + colnames(x)[k+1] <- 't' + } > x Veilingprijs Ouderdom Aanbieders 1 1235 127 13 2 1080 115 12 3 845 127 7 4 1522 150 9 5 1047 156 6 6 1979 182 11 7 1822 156 12 8 1253 132 10 9 1297 137 9 10 946 113 9 11 1713 137 15 12 1024 117 11 13 1147 137 8 14 1092 153 6 15 1152 117 13 16 1336 126 10 17 2131 170 14 18 1550 182 8 19 1884 162 11 20 2041 184 10 21 845 143 6 22 1483 159 9 23 1055 108 14 24 1545 175 8 25 729 108 6 26 1792 179 9 27 1175 111 15 28 1593 187 8 29 785 111 7 30 744 115 7 31 1356 194 5 32 1262 168 7 > k <- length(x[1,]) > df <- as.data.frame(x) > (mylm <- lm(df)) Call: lm(formula = df) Coefficients: (Intercept) Ouderdom Aanbieders -1338.95 12.74 85.95 > (mysum <- summary(mylm)) Call: lm(formula = df) Residuals: Min 1Q Median 3Q Max -206.49 -117.34 16.66 102.55 213.50 Coefficients: Estimate Std. Error t value Pr(>|t|) (Intercept) -1338.9513 173.8095 -7.704 1.71e-08 *** Ouderdom 12.7406 0.9047 14.082 1.69e-14 *** Aanbieders 85.9530 8.7285 9.847 9.34e-11 *** --- Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 Residual standard error: 133.5 on 29 degrees of freedom Multiple R-squared: 0.8923, Adjusted R-squared: 0.8849 F-statistic: 120.2 on 2 and 29 DF, p-value: 9.216e-15 > if (n > n25) { + kp3 <- k + 3 + nmkm3 <- n - k - 3 + gqarr <- array(NA, dim=c(nmkm3-kp3+1,3)) + numgqtests <- 0 + numsignificant1 <- 0 + numsignificant5 <- 0 + numsignificant10 <- 0 + for (mypoint in kp3:nmkm3) { + j <- 0 + numgqtests <- numgqtests + 1 + for (myalt in c('greater', 'two.sided', 'less')) { + j <- j + 1 + gqarr[mypoint-kp3+1,j] <- gqtest(mylm, point=mypoint, alternative=myalt)$p.value + } + if (gqarr[mypoint-kp3+1,2] < 0.01) numsignificant1 <- numsignificant1 + 1 + if (gqarr[mypoint-kp3+1,2] < 0.05) numsignificant5 <- numsignificant5 + 1 + if (gqarr[mypoint-kp3+1,2] < 0.10) numsignificant10 <- numsignificant10 + 1 + } + gqarr + } [,1] [,2] [,3] [1,] 0.61676019 0.7664796 0.3832398 [2,] 0.56916757 0.8616649 0.4308324 [3,] 0.46032136 0.9206427 0.5396786 [4,] 0.42973037 0.8594607 0.5702696 [5,] 0.36696167 0.7339233 0.6330383 [6,] 0.25326816 0.5065363 0.7467318 [7,] 0.17865755 0.3573151 0.8213424 [8,] 0.11513872 0.2302774 0.8848613 [9,] 0.07716865 0.1543373 0.9228313 [10,] 0.06104873 0.1220975 0.9389513 [11,] 0.13918100 0.2783620 0.8608190 [12,] 0.10579204 0.2115841 0.8942080 [13,] 0.11643994 0.2328799 0.8835601 [14,] 0.22983646 0.4596729 0.7701635 [15,] 0.45103833 0.9020767 0.5489617 [16,] 0.55056403 0.8988719 0.4494360 [17,] 0.49717677 0.9943535 0.5028232 [18,] 0.46895183 0.9379037 0.5310482 [19,] 0.37690181 0.7538036 0.6230982 [20,] 0.36302758 0.7260552 0.6369724 [21,] 0.84191899 0.3161620 0.1580810 > postscript(file="/var/www/wessaorg/rcomp/tmp/1566j1298402059.ps",horizontal=F,onefile=F,pagecentre=F,paper="special",width=8.3333333333333,height=5.5555555555556) > plot(x[,1], type='l', main='Actuals and Interpolation', ylab='value of Actuals and Interpolation (dots)', xlab='time or index') > points(x[,1]-mysum$resid) > grid() > dev.off() null device 1 > postscript(file="/var/www/wessaorg/rcomp/tmp/2vfsj1298402059.ps",horizontal=F,onefile=F,pagecentre=F,paper="special",width=8.3333333333333,height=5.5555555555556) > plot(mysum$resid, type='b', pch=19, main='Residuals', ylab='value of Residuals', xlab='time or index') > grid() > dev.off() null device 1 > postscript(file="/var/www/wessaorg/rcomp/tmp/30fwk1298402059.ps",horizontal=F,onefile=F,pagecentre=F,paper="special",width=8.3333333333333,height=5.5555555555556) > hist(mysum$resid, main='Residual Histogram', xlab='values of Residuals') > grid() > dev.off() null device 1 > postscript(file="/var/www/wessaorg/rcomp/tmp/48ow21298402059.ps",horizontal=F,onefile=F,pagecentre=F,paper="special",width=8.3333333333333,height=5.5555555555556) > densityplot(~mysum$resid,col='black',main='Residual Density Plot', xlab='values of Residuals') > dev.off() null device 1 > postscript(file="/var/www/wessaorg/rcomp/tmp/5pchz1298402059.ps",horizontal=F,onefile=F,pagecentre=F,paper="special",width=8.3333333333333,height=5.5555555555556) > qqnorm(mysum$resid, main='Residual Normal Q-Q Plot') > qqline(mysum$resid) > grid() > dev.off() null device 1 > (myerror <- as.ts(mysum$resid)) Time Series: Start = 1 End = 32 Frequency = 1 1 2 3 4 5 6 7 -161.49037 -77.65049 -35.77246 176.28837 -117.29612 53.68403 141.98597 8 9 10 11 12 13 14 50.66572 116.91583 71.68961 17.19792 -73.17866 52.86881 -34.07440 15 16 17 18 19 20 21 -117.08463 210.10916 100.71196 -117.45702 213.49551 176.15586 -153.66866 22 23 24 25 26 27 28 22.62320 -185.37244 -33.27300 176.25143 76.81172 -189.54715 -138.15989 29 30 31 32 108.07673 16.11443 -206.48496 -141.13600 > postscript(file="/var/www/wessaorg/rcomp/tmp/6rt8k1298402059.ps",horizontal=F,onefile=F,pagecentre=F,paper="special",width=8.3333333333333,height=5.5555555555556) > dum <- cbind(lag(myerror,k=1),myerror) > dum Time Series: Start = 0 End = 32 Frequency = 1 lag(myerror, k = 1) myerror 0 -161.49037 NA 1 -77.65049 -161.49037 2 -35.77246 -77.65049 3 176.28837 -35.77246 4 -117.29612 176.28837 5 53.68403 -117.29612 6 141.98597 53.68403 7 50.66572 141.98597 8 116.91583 50.66572 9 71.68961 116.91583 10 17.19792 71.68961 11 -73.17866 17.19792 12 52.86881 -73.17866 13 -34.07440 52.86881 14 -117.08463 -34.07440 15 210.10916 -117.08463 16 100.71196 210.10916 17 -117.45702 100.71196 18 213.49551 -117.45702 19 176.15586 213.49551 20 -153.66866 176.15586 21 22.62320 -153.66866 22 -185.37244 22.62320 23 -33.27300 -185.37244 24 176.25143 -33.27300 25 76.81172 176.25143 26 -189.54715 76.81172 27 -138.15989 -189.54715 28 108.07673 -138.15989 29 16.11443 108.07673 30 -206.48496 16.11443 31 -141.13600 -206.48496 32 NA -141.13600 > dum1 <- dum[2:length(myerror),] > dum1 lag(myerror, k = 1) myerror [1,] -77.65049 -161.49037 [2,] -35.77246 -77.65049 [3,] 176.28837 -35.77246 [4,] -117.29612 176.28837 [5,] 53.68403 -117.29612 [6,] 141.98597 53.68403 [7,] 50.66572 141.98597 [8,] 116.91583 50.66572 [9,] 71.68961 116.91583 [10,] 17.19792 71.68961 [11,] -73.17866 17.19792 [12,] 52.86881 -73.17866 [13,] -34.07440 52.86881 [14,] -117.08463 -34.07440 [15,] 210.10916 -117.08463 [16,] 100.71196 210.10916 [17,] -117.45702 100.71196 [18,] 213.49551 -117.45702 [19,] 176.15586 213.49551 [20,] -153.66866 176.15586 [21,] 22.62320 -153.66866 [22,] -185.37244 22.62320 [23,] -33.27300 -185.37244 [24,] 176.25143 -33.27300 [25,] 76.81172 176.25143 [26,] -189.54715 76.81172 [27,] -138.15989 -189.54715 [28,] 108.07673 -138.15989 [29,] 16.11443 108.07673 [30,] -206.48496 16.11443 [31,] -141.13600 -206.48496 > z <- as.data.frame(dum1) > z lag(myerror, k = 1) myerror 1 -77.65049 -161.49037 2 -35.77246 -77.65049 3 176.28837 -35.77246 4 -117.29612 176.28837 5 53.68403 -117.29612 6 141.98597 53.68403 7 50.66572 141.98597 8 116.91583 50.66572 9 71.68961 116.91583 10 17.19792 71.68961 11 -73.17866 17.19792 12 52.86881 -73.17866 13 -34.07440 52.86881 14 -117.08463 -34.07440 15 210.10916 -117.08463 16 100.71196 210.10916 17 -117.45702 100.71196 18 213.49551 -117.45702 19 176.15586 213.49551 20 -153.66866 176.15586 21 22.62320 -153.66866 22 -185.37244 22.62320 23 -33.27300 -185.37244 24 176.25143 -33.27300 25 76.81172 176.25143 26 -189.54715 76.81172 27 -138.15989 -189.54715 28 108.07673 -138.15989 29 16.11443 108.07673 30 -206.48496 16.11443 31 -141.13600 -206.48496 > plot(z,main=paste('Residual Lag plot, lowess, and regression line'), ylab='values of Residuals', xlab='lagged values of Residuals') > lines(lowess(z)) > abline(lm(z)) > grid() > dev.off() null device 1 > postscript(file="/var/www/wessaorg/rcomp/tmp/79cc81298402059.ps",horizontal=F,onefile=F,pagecentre=F,paper="special",width=8.3333333333333,height=5.5555555555556) > acf(mysum$resid, lag.max=length(mysum$resid)/2, main='Residual Autocorrelation Function') > grid() > dev.off() null device 1 > postscript(file="/var/www/wessaorg/rcomp/tmp/8daht1298402059.ps",horizontal=F,onefile=F,pagecentre=F,paper="special",width=8.3333333333333,height=5.5555555555556) > pacf(mysum$resid, lag.max=length(mysum$resid)/2, main='Residual Partial Autocorrelation Function') > grid() > dev.off() null device 1 > postscript(file="/var/www/wessaorg/rcomp/tmp/9oahj1298402059.ps",horizontal=F,onefile=F,pagecentre=F,paper="special",width=8.3333333333333,height=5.5555555555556) > opar <- par(mfrow = c(2,2), oma = c(0, 0, 1.1, 0)) > plot(mylm, las = 1, sub='Residual Diagnostics') > par(opar) > dev.off() null device 1 > if (n > n25) { + postscript(file="/var/www/wessaorg/rcomp/tmp/105tyq1298402059.ps",horizontal=F,onefile=F,pagecentre=F,paper="special",width=8.3333333333333,height=5.5555555555556) + plot(kp3:nmkm3,gqarr[,2], main='Goldfeld-Quandt test',ylab='2-sided p-value',xlab='breakpoint') + grid() + dev.off() + } null device 1 > > #Note: the /var/www/wessaorg/rcomp/createtable file can be downloaded at http://www.wessa.net/cretab > load(file="/var/www/wessaorg/rcomp/createtable") > > a<-table.start() > a<-table.row.start(a) > a<-table.element(a, 'Multiple Linear Regression - Estimated Regression Equation', 1, TRUE) > a<-table.row.end(a) > myeq <- colnames(x)[1] > myeq <- paste(myeq, '[t] = ', sep='') > for (i in 1:k){ + if (mysum$coefficients[i,1] > 0) myeq <- paste(myeq, '+', '') + myeq <- paste(myeq, mysum$coefficients[i,1], sep=' ') + if (rownames(mysum$coefficients)[i] != '(Intercept)') { + myeq <- paste(myeq, rownames(mysum$coefficients)[i], sep='') + if (rownames(mysum$coefficients)[i] != 't') myeq <- paste(myeq, '[t]', sep='') + } + } > myeq <- paste(myeq, ' + e[t]') > a<-table.row.start(a) > a<-table.element(a, myeq) > a<-table.row.end(a) > a<-table.end(a) > table.save(a,file="/var/www/wessaorg/rcomp/tmp/11cgll1298402059.tab") > a<-table.start() > a<-table.row.start(a) > a<-table.element(a,hyperlink('http://www.xycoon.com/ols1.htm','Multiple Linear Regression - Ordinary Least Squares',''), 6, TRUE) > a<-table.row.end(a) > a<-table.row.start(a) > a<-table.element(a,'Variable',header=TRUE) > a<-table.element(a,'Parameter',header=TRUE) > a<-table.element(a,'S.D.',header=TRUE) > a<-table.element(a,'T-STAT
H0: parameter = 0',header=TRUE) > a<-table.element(a,'2-tail p-value',header=TRUE) > a<-table.element(a,'1-tail p-value',header=TRUE) > a<-table.row.end(a) > for (i in 1:k){ + a<-table.row.start(a) + a<-table.element(a,rownames(mysum$coefficients)[i],header=TRUE) + a<-table.element(a,mysum$coefficients[i,1]) + a<-table.element(a, round(mysum$coefficients[i,2],6)) + a<-table.element(a, round(mysum$coefficients[i,3],4)) + a<-table.element(a, round(mysum$coefficients[i,4],6)) + a<-table.element(a, round(mysum$coefficients[i,4]/2,6)) + a<-table.row.end(a) + } > a<-table.end(a) > table.save(a,file="/var/www/wessaorg/rcomp/tmp/1271h01298402059.tab") > a<-table.start() > a<-table.row.start(a) > a<-table.element(a, 'Multiple Linear Regression - Regression Statistics', 2, TRUE) > a<-table.row.end(a) > a<-table.row.start(a) > a<-table.element(a, 'Multiple R',1,TRUE) > a<-table.element(a, sqrt(mysum$r.squared)) > a<-table.row.end(a) > a<-table.row.start(a) > a<-table.element(a, 'R-squared',1,TRUE) > a<-table.element(a, mysum$r.squared) > a<-table.row.end(a) > a<-table.row.start(a) > a<-table.element(a, 'Adjusted R-squared',1,TRUE) > a<-table.element(a, mysum$adj.r.squared) > a<-table.row.end(a) > a<-table.row.start(a) > a<-table.element(a, 'F-TEST (value)',1,TRUE) > a<-table.element(a, mysum$fstatistic[1]) > a<-table.row.end(a) > a<-table.row.start(a) > a<-table.element(a, 'F-TEST (DF numerator)',1,TRUE) > a<-table.element(a, mysum$fstatistic[2]) > a<-table.row.end(a) > a<-table.row.start(a) > a<-table.element(a, 'F-TEST (DF denominator)',1,TRUE) > a<-table.element(a, mysum$fstatistic[3]) > a<-table.row.end(a) > a<-table.row.start(a) > a<-table.element(a, 'p-value',1,TRUE) > a<-table.element(a, 1-pf(mysum$fstatistic[1],mysum$fstatistic[2],mysum$fstatistic[3])) > a<-table.row.end(a) > a<-table.row.start(a) > a<-table.element(a, 'Multiple Linear Regression - Residual Statistics', 2, TRUE) > a<-table.row.end(a) > a<-table.row.start(a) > a<-table.element(a, 'Residual Standard Deviation',1,TRUE) > a<-table.element(a, mysum$sigma) > a<-table.row.end(a) > a<-table.row.start(a) > a<-table.element(a, 'Sum Squared Residuals',1,TRUE) > a<-table.element(a, sum(myerror*myerror)) > a<-table.row.end(a) > a<-table.end(a) > table.save(a,file="/var/www/wessaorg/rcomp/tmp/13380r1298402059.tab") > a<-table.start() > a<-table.row.start(a) > a<-table.element(a, 'Multiple Linear Regression - Actuals, Interpolation, and Residuals', 4, TRUE) > a<-table.row.end(a) > a<-table.row.start(a) > a<-table.element(a, 'Time or Index', 1, TRUE) > a<-table.element(a, 'Actuals', 1, TRUE) > a<-table.element(a, 'Interpolation
Forecast', 1, TRUE) > a<-table.element(a, 'Residuals
Prediction Error', 1, TRUE) > a<-table.row.end(a) > for (i in 1:n) { + a<-table.row.start(a) + a<-table.element(a,i, 1, TRUE) + a<-table.element(a,x[i]) + a<-table.element(a,x[i]-mysum$resid[i]) + a<-table.element(a,mysum$resid[i]) + a<-table.row.end(a) + } > a<-table.end(a) > table.save(a,file="/var/www/wessaorg/rcomp/tmp/14m0g51298402059.tab") > if (n > n25) { + a<-table.start() + a<-table.row.start(a) + a<-table.element(a,'Goldfeld-Quandt test for Heteroskedasticity',4,TRUE) + a<-table.row.end(a) + a<-table.row.start(a) + a<-table.element(a,'p-values',header=TRUE) + a<-table.element(a,'Alternative Hypothesis',3,header=TRUE) + a<-table.row.end(a) + a<-table.row.start(a) + a<-table.element(a,'breakpoint index',header=TRUE) + a<-table.element(a,'greater',header=TRUE) + a<-table.element(a,'2-sided',header=TRUE) + a<-table.element(a,'less',header=TRUE) + a<-table.row.end(a) + for (mypoint in kp3:nmkm3) { + a<-table.row.start(a) + a<-table.element(a,mypoint,header=TRUE) + a<-table.element(a,gqarr[mypoint-kp3+1,1]) + a<-table.element(a,gqarr[mypoint-kp3+1,2]) + a<-table.element(a,gqarr[mypoint-kp3+1,3]) + a<-table.row.end(a) + } + a<-table.end(a) + table.save(a,file="/var/www/wessaorg/rcomp/tmp/15nld11298402059.tab") + a<-table.start() + a<-table.row.start(a) + a<-table.element(a,'Meta Analysis of Goldfeld-Quandt test for Heteroskedasticity',4,TRUE) + a<-table.row.end(a) + a<-table.row.start(a) + a<-table.element(a,'Description',header=TRUE) + a<-table.element(a,'# significant tests',header=TRUE) + a<-table.element(a,'% significant tests',header=TRUE) + a<-table.element(a,'OK/NOK',header=TRUE) + a<-table.row.end(a) + a<-table.row.start(a) + a<-table.element(a,'1% type I error level',header=TRUE) + a<-table.element(a,numsignificant1) + a<-table.element(a,numsignificant1/numgqtests) + if (numsignificant1/numgqtests < 0.01) dum <- 'OK' else dum <- 'NOK' + a<-table.element(a,dum) + a<-table.row.end(a) + a<-table.row.start(a) + a<-table.element(a,'5% type I error level',header=TRUE) + a<-table.element(a,numsignificant5) + a<-table.element(a,numsignificant5/numgqtests) + if (numsignificant5/numgqtests < 0.05) dum <- 'OK' else dum <- 'NOK' + a<-table.element(a,dum) + a<-table.row.end(a) + a<-table.row.start(a) + a<-table.element(a,'10% type I error level',header=TRUE) + a<-table.element(a,numsignificant10) + a<-table.element(a,numsignificant10/numgqtests) + if (numsignificant10/numgqtests < 0.1) dum <- 'OK' else dum <- 'NOK' + a<-table.element(a,dum) + a<-table.row.end(a) + a<-table.end(a) + table.save(a,file="/var/www/wessaorg/rcomp/tmp/16ne941298402059.tab") + } > > try(system("convert tmp/1566j1298402059.ps tmp/1566j1298402059.png",intern=TRUE)) character(0) > try(system("convert tmp/2vfsj1298402059.ps tmp/2vfsj1298402059.png",intern=TRUE)) character(0) > try(system("convert tmp/30fwk1298402059.ps tmp/30fwk1298402059.png",intern=TRUE)) character(0) > try(system("convert tmp/48ow21298402059.ps tmp/48ow21298402059.png",intern=TRUE)) character(0) > try(system("convert tmp/5pchz1298402059.ps tmp/5pchz1298402059.png",intern=TRUE)) character(0) > try(system("convert tmp/6rt8k1298402059.ps tmp/6rt8k1298402059.png",intern=TRUE)) character(0) > try(system("convert tmp/79cc81298402059.ps tmp/79cc81298402059.png",intern=TRUE)) character(0) > try(system("convert tmp/8daht1298402059.ps tmp/8daht1298402059.png",intern=TRUE)) character(0) > try(system("convert tmp/9oahj1298402059.ps tmp/9oahj1298402059.png",intern=TRUE)) character(0) > try(system("convert tmp/105tyq1298402059.ps tmp/105tyq1298402059.png",intern=TRUE)) character(0) > > > proc.time() user system elapsed 3.000 0.390 3.548