Tips in MATLAB

Number operation and matrix operation

.* : Is the multiplication or division of the corresponding elements ; Point multiplication requires that the two involved in the operation must have the same dimension ;

* : Is matrix multiplication or division ; The dimension of the column of the former matrix is required to be equal to the dimension of the row of the latter matrix .

.^： Is to multiply each element . such as A It's a matrix ,A^2=A*A,

^: Such as ：A.^2=B,B by A A matrix in which all elements are squared , to A One of the aij,B The corresponding position in is aij^2

mapping

Draw a piecewise curve

%1   to  X  assignment 
x = -70 : 0.01 : 65;
%2  to  Y  Assign and determine  X  The range of ; The interval method is   function .*( Section );
y2 =
(6+sqrt(20*20-(x+40).*(x+40))).*(x>=-70&x<-62)+
(15+sqrt(10*10-(x+50).*(x+50))).*(x>=-62&x<-49)+
(9+sqrt(12*12-(x+56).*(x+56))).*(x>=-49&x<-39)+
(-tan(23/18)*x-92).*(x>=-39&x<-38)+
(16-sqrt(11*11-(x+25).*(x+25))).*(x>=-38&x<-29)+
(100-sqrt(100*100-(x+1.25).*(x+1.25))).*(x>=-29&x<-9)+
(498.975-sqrt(500*500-(x-32).*(x-32))).*(x>=-9&x<20)+
(-220+sqrt(220*220-(x-15).*(x-15))).*(x>=20&x<42)+
(-0.125*x+2).*(x>=42.&x<60)+
25.*(x>=60&x<=65);
%3 plot
plot(x,y2);

Be careful ：matlab Be sure to write a long line ！ Cannot write in segments , Otherwise an error .