error with bar !!

l=8;w=5;
ra=w;m=w*1;
x=sym('x');
x=0:0.1:1;
bar(x,sfx,'r','linewidth',5)
bmx=-w*x;
bar(x,bmx)

i tried changing the path and name also then ran it again, the error is showing:

Error using bar (line 127)

Unable to convert expression into double array.

Error in q1 (line 5)

bar(x,sfx,'r','linewidth',5)

[Walter Roberson]

sfx is not defined in that code.