xgraph installation problem on Linux

[NIKOLAOS GEORGANOPOULOS <nikolaos.georganopoulos@kcl.ac.uk>]

I am trying to compile xgraph on Linux and I get the following error.
I have run the patches to fix other problems.
I have also changed the path in the MAkefile for the libXext.a and
relevant files but still gives me an error.
Any suggestions?

Thanks in advance! 

Nikos


cc    -I/usr/include         -c xgraph.c -o xgraph.o
xgraph.c: In function `main':
xgraph.c:113: warning: passing arg 1 of `XSetErrorHandler' from
incompatible poi
nter type
cc    -I/usr/include         -c xgX.c -o xgX.o
cc    -I/usr/include         -c hard_devices.c -o hard_devices.o
cc    -I/usr/include         -c dialog.c -o dialog.o
cc    -I/usr/include         -c hpgl.c -o hpgl.o
hpgl.c: In function `hpglInit':
hpgl.c:75: warning: return makes integer from pointer without a cast
cc    -I/usr/include         -c ps.c -o ps.o
cc    -I/usr/include         -c idraw.c -o idraw.o
cc    -I/usr/include         -c xtb.c -o xtb.o
xtb.c: In function `xtb_lookup':
xtb.c:217: warning: passing arg 4 of `XFindContext' from incompatible
pointer ty
pe
cc    -I/usr/include         -c st.c -o st.o
cc    -I/usr/include         -c params.c -o params.o
cc    -I/usr/include         -c alloc.c -o alloc.o
cc    -I/usr/include         -c draw.c -o draw.o
cc    -I/usr/include         -c init.c -o init.o
init.c: In function `InitSets':
init.c:143: warning: passing arg 2 of `param_init' makes integer from
pointer wi
thout a cast
cc    -I/usr/include         -c read.c -o read.o
cc    -I/usr/include         -c tgif.c -o tgif.o
cc    -I/usr/include         -c derivative.c -o derivative.o
rm -f xgraph
cc -o xgraph xgraph.o xgX.o hard_devices.o dialog.o hpgl.o ps.o idraw.o
xtb.o st
.o params.o alloc.o draw.o init.o read.o tgif.o derivative.o   -lXext
-lX11 -lm 

/usr/bin/ld: cannot open -lXext: No such file or directory
collect2: ld returned 1 exit status
make: *** [xgraph] Error 1