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xwndf250

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Á÷Ðв¡Ä£ÐÍ sir
dI/dt=a*S*I-b*I
dS/dt=-a*S*I
dR/dt=b*I
S+I+R=1ÇÒ0 ÏëÒª×öÒ»¸öºá×ø±êt=[0,50]£¬ ×Ý×ø±êdI/dt¡¢dS/dt¡¢dR/dtµÄ3ÌõÇúÏߣ¬Çó¾ßÌå³ÌÐò£¬±¾ÈËдµÄ³ÌÐò
mÎļþ£ºfunction y=SIR(t,x)
a=0.2;b=0.1;
y=[a*x(1)*x(2)-b*x(1);
-a*x(1)*x(2);
b*x(3)];
end
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csgt0

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dbb627: ½ð±Ò+2, ¸ÐлӦÖú 2013-02-26 14:07:58
CODE:
function xwn
options = odeset('RelTol',1e-4,'AbsTol',[1e-4 1e-4 1e-5]);
intvalue=[0.1 0.4 0.5];       %t=0ʱµÄ³õÖµ
[T,Y] = ode45(@rigid,[0 50],intvalue,options);
plot(T,Y(:,1),'-',T,Y(:,2),'-.',T,Y(:,3),'.')
title('T-Yͼ')
for i=1:length(T)     
vdy(:,i)=rigid(T(i),Y(i,:));
end
figure
plot(T,vdy(1,:),'-',T,vdy(2,:),'-.',T,vdy(3,:),'.')
title('T-dYͼ')
end

function dy = rigid(t,y)
dy = zeros(3,1);    % a column vector
a=0.2;
b=0.1;
dy(1) = a*y(2)*y(1)-b * y(1);
dy(2) = -a*y(2) * y(1);
dy(3) = b * y(1);
end

showmethemoney
2Â¥2013-02-26 11:06:11
ÒÑÔÄ   »Ø¸´´ËÂ¥   ¹Ø×¢TA ¸øTA·¢ÏûÏ¢ ËÍTAºì»¨ TAµÄ»ØÌû

xwndf250

Òø³æ (СÓÐÃûÆø)

ÒýÓûØÌû:
2Â¥: Originally posted by csgt0 at 2013-02-26 11:06:11
function xwn
options = odeset('RelTol',1e-4,'AbsTol',);
intvalue=;       %t=0ʱµÄ³õÖµ
= ode45(@rigid,,intvalue,options);
plot(T,Y(:,1),'-',T,Y(:,2),'-.',T,Y(:,3),'.')
title('T-Yͼ')
for i=1: ...

function dy = rigid(t,y)ºóÃæµÄÎÒ¿´¶®ÁË£¬µ«ÊÇÇ°Ãæfunction xwnûÓп´¶®£¬ÎҼǵÃÇóµ¼Ã²ËÆÓÃdiffº¯ÊýµÄ£¬Äܲ»ÄÜÏêϸ½²½âÏÂodeset£¨£©º¯Êý£¬intvalue×÷Ó㬡°for i=1:length(T) ºÍvdy(:,i)=rigid(T(i),Y(i,);¡±µÄÒâ˼¡£ÎÒÊÇС°×£¬ÇóÖ¸½Ì¡£ºÃµÄ»°ÎÒ¶à¸ø½ð±Ò¡£
3Â¥2013-02-26 21:06:43
ÒÑÔÄ   »Ø¸´´ËÂ¥   ¹Ø×¢TA ¸øTA·¢ÏûÏ¢ ËÍTAºì»¨ TAµÄ»ØÌû

csgt0

ÈÙÓþ°æÖ÷ (ÖøÃûдÊÖ)

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¡¾´ð°¸¡¿Ó¦Öú»ØÌû

¡ï ¡ï ¡ï ¡ï ¡ï ¡ï ¡ï ¡ï ¡ï ¡ï ¡ï ¡ï ¡ï ¡ï ¡ï ¡ï
xwndf250: ½ð±Ò+15, ¡ï¡ï¡ïºÜÓаïÖú, ·Ç³£¸ÐлÄúµÄ°ïÖú£¬¸øÄú½ð±Ò£¬Ë³±ãÎÊÏ£¬t0³õÖµÔõôȷ¶¨µÄ£¿Ò²¾ÍÊÇ0.1£¬0.4£¬0.5ÊÇÔõôȷ¶¨µÄ£¿ 2013-02-27 10:00:25
fegg7502: ½ð±Ò+1, Ó¦ÖúÖ¸Êý+1, ¹ÄÀø½»Á÷ 2013-04-02 09:30:14
odeset£¨£©º¯ÊýÉèÖÃÊýÖµ½âµÄ¼ÆË㾫¶È£¬Æäʵһ°ã²»ÓÃÒ²¿ÉÒÔ
intvalueÊdzõÖµ°¡£¬t=0ʱµÄ³õÖµ
¡°for i=1:length(T) ºÍvdy(:,i)=rigid(T(i),Y(i,);¡±µÄΪÁËÑ­»·¼ÆËãÿ¸ötϵÄ3¸öµ¼ÊýÖµ
showmethemoney
4Â¥2013-02-27 09:54:46
ÒÑÔÄ   »Ø¸´´ËÂ¥   ¹Ø×¢TA ¸øTA·¢ÏûÏ¢ ËÍTAºì»¨ TAµÄ»ØÌû

csgt0

ÈÙÓþ°æÖ÷ (ÖøÃûдÊÖ)

²ÊÉ«¹Òͼ

¡¾´ð°¸¡¿Ó¦Öú»ØÌû

¡ï
fegg7502: ½ð±Ò+1, Ó¦ÖúÖ¸Êý+1, ¹ÄÀø½»Á÷ 2013-04-02 09:30:24
ÒýÓûØÌû:
3Â¥: Originally posted by xwndf250 at 2013-02-26 21:06:43
function dy = rigid(t,y)ºóÃæµÄÎÒ¿´¶®ÁË£¬µ«ÊÇÇ°Ãæfunction xwnûÓп´¶®£¬ÎҼǵÃÇóµ¼Ã²ËÆÓÃdiffº¯ÊýµÄ£¬Äܲ»ÄÜÏêϸ½²½âÏÂodeset£¨£©º¯Êý£¬intvalue×÷Ó㬡°for i=1:length(T) ºÍvdy(:,i)=rigid(T(i),Y(i,);¡±µÄ ...

¾ÍÊÇt=0ÊǵÄISR°¡£¬¾ßÌå¶àÉٵÿ´ÄãµÄʵ¼ÊÇé¿ö£¬ÎÒÖ»ÊÇËæÒâдµÄ¸öÊý¡£
showmethemoney
5Â¥2013-02-27 10:37:52
ÒÑÔÄ   »Ø¸´´ËÂ¥   ¹Ø×¢TA ¸øTA·¢ÏûÏ¢ ËÍTAºì»¨ TAµÄ»ØÌû

xwndf250

Òø³æ (СÓÐÃûÆø)

ÒýÓûØÌû:
5Â¥: Originally posted by csgt0 at 2013-02-27 10:37:52
¾ÍÊÇt=0ÊǵÄISR°¡£¬¾ßÌå¶àÉٵÿ´ÄãµÄʵ¼ÊÇé¿ö£¬ÎÒÖ»ÊÇËæÒâдµÄ¸öÊý¡£...

ºÃµÄ ллÄã
6Â¥2013-02-27 11:09:25
ÒÑÔÄ   »Ø¸´´ËÂ¥   ¹Ø×¢TA ¸øTA·¢ÏûÏ¢ ËÍTAºì»¨ TAµÄ»ØÌû

657801288

Ìú³æ (³õÈëÎÄ̳)

ÒýÓûØÌû:
2Â¥: Originally posted by csgt0 at 2013-02-26 11:06:11
function xwn
options = odeset('RelTol',1e-4,'AbsTol',);
intvalue=;       %t=0ʱµÄ³õÖµ
= ode45(@rigid,,intvalue,options);
plot(T,Y(:,1),'-',T,Y(:,2),'-.',T,Y(:,3),'.')
title('T-Yͼ')
for i=1: ...

ÄãºÃ£¬Á½ÖÖ·½·¨×ö³öµÄͼÔõô²»Ò»ÑùÄØ£¿ÇóÖ¸½Ì¡£
7Â¥2013-03-30 08:49:39
ÒÑÔÄ   »Ø¸´´ËÂ¥   ¹Ø×¢TA ¸øTA·¢ÏûÏ¢ ËÍTAºì»¨ TAµÄ»ØÌû

csgt0

ÈÙÓþ°æÖ÷ (ÖøÃûдÊÖ)

²ÊÉ«¹Òͼ

¡¾´ð°¸¡¿Ó¦Öú»ØÌû

¡ï
fegg7502: ½ð±Ò+1, Ó¦ÖúÖ¸Êý+1, ¹ÄÀø½»Á÷ 2013-04-02 09:30:38
²»ÊÇÁ½ÖÖ·½·¨°¡£¬Ç°Ãæ»­µÄÊÇT-Yͼ£¬ºóÃæÊÇÄãÒªµÄT-dYͼ¡£
showmethemoney
8Â¥2013-04-01 10:48:30
ÒÑÔÄ   »Ø¸´´ËÂ¥   ¹Ø×¢TA ¸øTA·¢ÏûÏ¢ ËÍTAºì»¨ TAµÄ»ØÌû
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