1 Do hoa trong khong gian hai chieu.

1.1 Cac lenh ve co ban

De ve mot do thi co ban trong mat phang ta dung cau lenh plot. Lenh plot nay se ve do thi cua mot mang du lieu trong he truc thich hop va noi cac diem bang d­ong thang.

Vi du:

>> x=(1:0.1:7);

>> y=2*x.^2-x;

>> plot(x,y)

Ket qua se la

(*) Mot so lenh ve co ban

Ten lenhnghia

plot(x,y) Ve theo vector y va x (y ruc tung cua he, xtruc hoanh). Do thi tu d­oc se la tap cua cac diem (xi,yi)

plot(A,B) Voi A,B la cac ma tran. Ve cac cot cua A theo cac cot cua B. Neu A va B la 2 ma tran co cung do lon mxn thi ta se thu d­oc m do thi n diem.

plot(....,str) Ve do thi voi cac chi so ve mau sac va kieu d­ong theo bien str.

Ta co bang ve kieu d­ong va mau do thi nh­ sau.

Kieu du­ong Cach the hien Kieu du­ong Cach the hien

'' diem-­ong lien net - du­ong lien net

* sao --­ duong dut net

X chu cai x -.­ duong cham gach

O chu cai o :­ duong cham

+ dau cong

Ki hieu Mau the hien Ki hieu Mau the hien

Y vang C xanh la ma

G xanh la cay W trang

M do t­oi R do

B xanh lam K den

Vi du:

Ve do thi y=x3 voi mau la mau xanh va kieu du­ong +

>> x=linspace(1,100,100);

>> y=x.*x.*x;

>> plot(x,y,'b+')