ggplot2 - Extracting x-axis intercept from a linear fit in R -


i have data generated using following lines of code,

x <- c(1:10) y <- x^3 z <- y-20 s <- z/3 t <- s*6 q <- s*y x1 <- cbind(x,y,z,s,t,q) x1 <- data.frame(x1)

i plot x versus y,s, , t melt data frame x1 first,

 library(reshape2)   xm <- melt(x1, id=names(x1)[1], measure=names(x1)[c(2, 4, 5)], variable = "cols"`)

then plot them along linear fits using following code,

library(ggplot2) plt <- ggplot(xm, aes(x = x, y = value, color = cols)) +   geom_point(size = 3) +   labs(x = "x", y = "y") +    geom_smooth(method = "lm", se = false) plt

the plot generated shown below,

enter image description here

now liked interpolate x-intercept of linear fit. point in plot y axis value 0.

the following lines of code shown here, extracts slope , y-intercept.

fits <- by(xm[-2], xm$cols, function(i) coef(lm(value ~ x, i))) data.frame(cols = names(fits), do.call(rbind, fits))

is there way how can extract x-intercept other manually calculating slope , y-intercept?

thanks help!

you inverse prediction implemented in package chemcal calibrations if don't want calculate yourself:

library(chemcal) res <- by(xm[-2], xm$cols, function(i) inverse.predict(lm(value ~ x, i), 0)$prediction) res[1:3] #xm$cols #y        s        t  #2.629981 2.819734 2.819734

edit:

maybe prefer this:

library(plyr) res <- ddply(xm, .(cols),    function(i) data.frame(xinter=inverse.predict(lm(value ~ x, i), 0)$prediction)) #   cols   xinter # 1    y 2.629981 # 2    s 2.819734 # 3    t 2.819734

Comments

Post a Comment

Popular posts from this blog

apache - Remove .php and add trailing slash in url using htaccess not loading css -

i have add following code htaccess file removing .php extension , add trailing slash urls. worked fine reduced page loading speed , css code not loading @ all. pages ugly. please help rewriteengine on rewritebase / ## hide .php extension snippet # externally redirect /dir/foo.php /dir/foo rewritecond %{the_request} ^[a-z]{3,}\s([^.]+)\.php [nc] rewriterule ^ %1/ [r,l] # add trailing slash rewritecond %{request_filename} !-f rewritecond %{request_uri} !/$ rewriterule . %{request_uri}/ [l,r=301] # internally forward /dir/foo /dir/foo.php rewritecond %{request_filename} !-d rewritecond %{request_filename}.php -f rewriterule ^(.*?)/?$ $1.php [l] we can rewrite urls using .htaccess files. before writing in .htaccess files need verify kind of server using. can check server adding a <?php phpinfo(); ?> in php page. ensure mod_rewrite module enabled in apache server. can identified checking phpinfo included page. common methods used url rewriting follows ...
Read more

inno setup - TLabel or TNewStaticText - change .Font.Style on Focus like Cursor changes with .Cursor -

is possible change .font.style on focus tlabel or tnewstatictext happens cursor when use .cursor ? there no built-in support track mouse hovering in inno setup @ time. however, intercepting window procedure of controls can track yourself. following example need innocallback library: [setup] appname=my program appversion=1.5 defaultdirname={pf}\my program outputdir=userdocs:inno setup examples output [files] source: "innocallback.dll"; destdir: "{tmp}"; flags: dontcopy [code] #ifdef unicode #define aw "w" #else #define aw "a" #endif const gwl_wndproc = -4; wm_mousemove = $0200; type wparam = uint_ptr; lparam = longint; lresult = longint; twindowproc = function(hwnd: hwnd; umsg: uint; wparam: wparam; lparam: lparam): lresult; function setcapture(hwnd: hwnd): hwnd; external 'setcapture@user32.dll stdcall'; function releasecapture: bool; external 'releasecapture@user32.dll stdcall'; func...
Read more