matlab中函数拟合方法个人总结_精品文档Word格式文档下载.doc
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p1995=interp1(year,product,1995)
%使用一维数据内插值(该题中只能在1900和2010之间进行插值,大于2010和小于1900都%无效)命令
x=1900:
1:
2010
y=interp1(year,product,x,'
spine'
);
plot(year,product,'
o'
x,y)
插值说明:
interp1(x,Y,xi,method)%用指定的算法计算插值:
’nearest’:
最近邻点插值,直接完成计算;
’linear’:
线性插值(缺省方式),直接完成计算;
’spine’:
三次样条函数插值。
对于该方法,命令interp1调用函数spline、ppval、mkpp、umkpp。
这些命令生成一系列用于分段多项式操作的函
数。
命令spline用它们执行三次样条函数插值;
’pchip’:
分段三次Hermite插值。
对于该方法,命令interp1调用函数pchip,用于对向量x与y执行分段三次内插值。
该方法保留单调性与
数据的外形;
’cubic’:
与’pchip’操作相同;
’v5cubic’:
在MATLAB5.0中的三次插值。
对于超出x范围的xi的分量,使用方法’nearest’、’linear’、’v5cubic’的插值算法,相应地将返回NaN。
对其他的方法,interp1将对超出的分量执行外插值算法。
yi=interp1(x,Y,xi,method,'
extrap'
)%对于超出x范围的xi中的分量将执行特殊的外插值法extrap。
yi=interp1(x,Y,xi,method,extrapval)%确定超出x范围的xi中的分量的外插值extrapval,其值通常取NaN或0。
例1
clear;
x=0:
10;
y=x.*sin(x);
xx=0:
.25:
yy=interp1(x,y,xx)
plot(x,y,'
kd'
xx,yy)
interp2
二维数据内插值(表格查找)
[X,Y]=meshgrid(-3:
3);
Z=peaks(X,Y);
[XI,YI]=meshgrid(-3:
.125:
ZZ=interp2(X,Y,Z,XI,YI);
surfl(X,Y,Z);
holdon;
surfl(XI,YI,ZZ+15)
axis([-33-33-520]);
shadingflat
holdoff
功能三维数据插值interp3(查表)
[x,y,z,v]=flow(20);
[xx,yy,zz]=meshgrid(.1:
10,-3:
3,-3:
vv=interp3(x,y,z,v,xx,yy,zz);
slice(xx,yy,zz,vv,[69.5],[12],[-2.2]);
shadinginterp;
colormapcool
等高线
Z=peaks
forw=1:
100
V=[w/10,0,w/10]
contour(Z,V)
%C=contour(Z,V)
%Clabel(C)
Holdon
title('
等高线及其标注'
)
end
三维曲面
x=0:
10
y=0:
.1:
1
[d,B]=meshgrid(x,y)
z=1./(B.*d.^2+1);
surf(B,d,z)
0.05:
[X,Y]=meshgrid(x,y)
Z=(X.^3+3.*Y.^2+5*Y);
%Z=(X.^2+3.*Y.^3+5*Y);
%
surf(X,Y,Z)
%一张普通的三维曲面,有时需要旋转一下才能看到下图的结果;
Z=(X.^2-Y.^2);
%Z=(4*X.^3*Y-4*X.*Y.^3);
surf(X,Y,Z)%一张普通的三维曲面,有时需要旋转一下才能看到下图的结果;
等高线2
x=-2:
0.1:
2
y=-2:
Z=(X.^2+Y.^2).^0.5
V=[w/3,w/pi,w/3]
holdon
三维曲面2
x=-5:
5
y=-5:
Z=1./((X+1).^2+(Y+1).^2+1)-1.5./((X-1).^2+(Y-1).^2+1)
mesh(X,Y,Z)
A=[1.486,3.059,0.1;
2.121,4.041,0.1;
2.570,3.959,0.1;
3.439,4.396,0.1;
4.505,3.012,0.1;
3.402,1.604,0.1;
2.570,2.065,0.1;
2.150,1.970,0.1;
1.794,3.059,0.2;
2.121,3.615,0.2;
2.570,3.473,0.2;
3.421,4.160,0.2;
4.271,3.036,0.2;
3.411,1.876,0.2;
2.561,2.562,0.2;
2.179,2.420,0.2;
2.757,3.024,0.3;
3.439,3.970,0.3;
4.084,3.036,0.3;
3.402,2.077,0.3;
2.879,3.036,0.4;
3.421,3.793,0.4;
3.953,3.036,0.4;
3.402,2.219,0.4;
3.000,3.047,0.5;
3.430,3.639,0.5;
3.822,3.012,0.5;
3.411,2.385,0.5;
3.103,3.012,0.6;
3.430,3.462,0.6;
3.710,3.036,0.6;
3.402,2.562,0.6;
3.224,3.047,0.7;
3.411,3.260,0.7;
3.542,3.024,0.7;
3.393,2.763,0.7];
x=A(:
1);
y=A(:
2);
z=A(:
3);
scatter(x,y,5,z)%散点图
figure
[X,Y,Z]=griddata(x,y,z,linspace(1.486,4.271)'
linspace(1.604,4.276),'
v4'
%插值
pcolor(X,Y,Z);
shadinginterp%伪彩色图
figure,contourf(X,Y,Z)%等高线图
A=[1.486,3.059,1858;
2.121,4.041,1858;
2.570,3.959,1858;
3.439,4.396,1858;
4.505,3.012,1858;
3.402,1.604,1858;
2.570,2.065,1858;
2.150,1.970,1858;
1.794,3.059,2350;
2.121,3.615,2350;
2.570,3.473,2350;
3.421,4.160,2350;
4.271,3.036,2350;
3.411,1.876,2350;
2.561,2.562,2350;
2.179,2.420,2350;
2.757,3.024,2600;
3.439,3.970,2600;
4.084,3.036,2600;
3.402,2.077,2600;
2.879,3.036,2849;
3.421,3.793,2849;
3.953,3.036,2849;
3.402,2.219,2849;
3.000,3.047,3010;
3.430,3.639,3010;
3.822,3.012,3010;
3.411,2.385,3010;
3.103,3.012,3345;
3.430,3.462,3345;
3.710,3.036,3345;
3.402,2.562,3345;
3.224,3.047,3629;
3.411,3.260,3629;
3.542,3.024,3629;
3.393,2.763,3629];
scatter(x,y,5,z)%散点图,5是点的大小
figure%打开显示图的界面
figure;
contourf(X,Y,Z)%等高线图
A=[1.109,1.059,1718;
2.021,0.841,1758;
2.870,0.359,1858;
4.039,0.196,1838;
4.505,3.012,3345;
3.402,1.604,3347;
2.570,2.065,3629;
2.150,1.970,3330;
1.794,3.059,2250;
2.121,3.615,3027;
2.570,3.473,2935;
3.421,4.160,1930;
4.271,3.036,2050;
3.411,1.876,3144;
2.561,2.562,3739;
2.179,2.420,1950;
2.757,3.024,3530;
3.439,3.970,2720;
4.084,3.036,2610;
3.402,2.077,3500;
2.879,3.036,3249;
3.421,3.793,2149;
3.822,3.012,2310;
3.411,2.385,3410;
3.430,3.462,3845;
3.710,3.036,2645;
3.402,2.562,2745;
3.224,3.047,3229;
3.411,3.260,3329;
3.542,3.024,3429;
3.393,2.763,3529];
sc