Hi List, Can someone help me to calculate the coordinates of the red and green points? In this example I found their approximate location by trying, but as I have to analyse many similar curves, I?d rather calculate the exact location. data<- c(0.008248005, 0.061242387, 0.099095516, 0.189943027, 0.227796157, 0.258078661, 0.280790538, 0.303502416, 0.386779301, 0.454914934, 0.545762445, 0.591186201, 0.682033712, 0.757739971, 0.825875604, 0.848587482, 0.803163726, 0.833446230, 0.878869985, 0.871299359, 0.878869985, 0.947005619, 1.000000000, 0.992429374, 0.954576245, 0.894011237, 0.765310597, 0.621468704, 0.492768064, 0.333784920, 0.258078661, 0.174801775, 0.099095516, 0.008248005) plot(data, type="l") abline(h=0.9) points(21.35,.9, pch=20, col="red") points(26,.9, pch=20, col="green") Thank you, Tonja ___________________________________________________________ Neu: WEB.DE De-Mail - Einfach wie E-Mail, sicher wie ein Brief! Jetzt De-Mail-Adresse reservieren: https://produkte.web.de/go/demail02
intercept point coordinates
2 messages · Tonja Krueger, Peter Ehlers
On 2011-01-17 04:14, Tonja Krueger wrote:
Hi List, Can someone help me to calculate the coordinates of the red and green points? In this example I found their approximate location by trying, but as I have to analyse many similar curves, I?d rather calculate the exact location. data<- c(0.008248005, 0.061242387, 0.099095516, 0.189943027, 0.227796157, 0.258078661, 0.280790538, 0.303502416, 0.386779301, 0.454914934, 0.545762445, 0.591186201, 0.682033712, 0.757739971, 0.825875604, 0.848587482, 0.803163726, 0.833446230, 0.878869985, 0.871299359, 0.878869985, 0.947005619, 1.000000000, 0.992429374, 0.954576245, 0.894011237, 0.765310597, 0.621468704, 0.492768064, 0.333784920, 0.258078661, 0.174801775, 0.099095516, 0.008248005) plot(data, type="l") abline(h=0.9) points(21.35,.9, pch=20, col="red") points(26,.9, pch=20, col="green") Thank you, Tonja
You can do this with graphics, using the locator() function: plot(data, type="l") abline(h=0.9) v <- locator(2) Now click on the intersection points and then extract v$x. It's best to blow up the relevant region of the plot (perhaps for each point separately) with appropriate xlim/ylim settings and to maximize your plot window. Alternatively, you can identify that the points lie in data[21:22] and in data[25:26]. Then use the approx() function: approx(data[21:22], 21:22, xout = 0.9) approx(data[25:26], 25:26, xout = 0.9) Your points were close - just a bit high: approx gives 21.31012 and 25.90112. Peter Ehlers