回覆列表
  • 1 # 愛逗的小夥伴

    你要知道,你要擬合的是一個分段函式,這本身就不是一般的連續光滑函式。

    nlinfit之所以要有初值這一項,就是考慮到在某些變態的情況下,無法找到最小二乘函式的最小值,可能是一個區域性的最小值,也可能根本找不到,所以有必要透過改變迭代初值的方法進行試驗。對於這種分段函式,最好的方法還是分段擬合。

    fun1=inline("4.213-300*x/ref(1)-300*(ref(2)+ref(3))+300*ref(3)*exp(-x/(ref(3)*ref(4)))","ref","x");

    fun2=inline("4.213-3000/ref(1)-300*ref(3)*exp(-x/(ref(3)*ref(4)))*(exp(10/(ref(3)*ref(4)))-1)","ref","x");

    fun=@(ref,t)((t<=10).*fun1(ref,t)+(t>10).*fun2(ref,t));

    t=0:0.1:50;

    v=[3.969

    3.963

    3.959

    3.955

    3.952

    3.949

    3.947

    3.945

    3.943

    3.941

    3.939

    3.938

    3.936

    3.935

    3.933

    3.932

    3.93

    3.929

    3.928

    3.927

    3.926

    3.925

    3.923

    3.922

    3.921

    3.92

    3.919

    3.918

    3.917

    3.916

    3.915

    3.914

    3.913

    3.912

    3.911

    3.91

    3.909

    3.908

    3.907

    3.907

    3.906

    3.905

    3.904

    3.903

    3.903

    3.902

    3.901

    3.9

    3.9

    3.899

    3.898

    3.898

    3.897

    3.896

    3.896

    3.895

    3.894

    3.893

    3.893

    3.892

    3.891

    3.891

    3.89

    3.889

    3.889

    3.888

    3.888

    3.887

    3.887

    3.886

    3.886

    3.885

    3.884

    3.884

    3.883

    3.882

    3.882

    3.881

    3.88

    3.88

    3.879

    3.879

    3.878

    3.878

    3.877

    3.877

    3.876

    3.876

    3.875

    3.875

    3.874

    3.874

    3.873

    3.873

    3.872

    3.872

    3.871

    3.87

    3.87

    3.869

    3.869

    4.105

    4.108

    4.11

    4.112

    4.114

    4.115

    4.116

    4.117

    4.118

    4.119

    4.119

    4.12

    4.12

    4.121

    4.122

    4.122

    4.123

    4.123

    4.124

    4.124

    4.124

    4.125

    4.125

    4.126

    4.126

    4.126

    4.127

    4.127

    4.128

    4.128

    4.129

    4.129

    4.129

    4.129

    4.129

    4.13

    4.13

    4.13

    4.13

    4.13

    4.131

    4.131

    4.131

    4.131

    4.132

    4.132

    4.132

    4.132

    4.132

    4.132

    4.133

    4.133

    4.133

    4.133

    4.133

    4.134

    4.134

    4.134

    4.134

    4.134

    4.134

    4.135

    4.135

    4.135

    4.135

    4.135

    4.136

    4.136

    4.136

    4.136

    4.136

    4.137

    4.137

    4.138

    4.138

    4.138

    4.139

    4.139

    4.139

    4.139

    4.139

    4.14

    4.14

    4.14

    4.14

    4.14

    4.14

    4.14

    4.14

    4.14

    4.14

    4.14

    4.14

    4.14

    4.14

    4.14

    4.14

    4.14

    4.14

    4.14

    4.14

    4.14

    4.14

    4.14

    4.14

    4.141

    4.141

    4.141

    4.141

    4.141

    4.141

    4.141

    4.141

    4.141

    4.141

    4.142

    4.142

    4.142

    4.142

    4.142

    4.142

    4.142

    4.142

    4.142

    4.142

    4.143

    4.143

    4.143

    4.143

    4.143

    4.143

    4.143

    4.143

    4.143

    4.143

    4.143

    4.143

    4.143

    4.144

    4.144

    4.144

    4.144

    4.144

    4.144

    4.144

    4.144

    4.144

    4.144

    4.144

    4.145

    4.145

    4.145

    4.145

    4.145

    4.145

    4.145

    4.145

    4.145

    4.145

    4.145

    4.145

    4.145

    4.145

    4.145

    4.145

    4.146

    4.146

    4.146

    4.146

    4.146

    4.146

    4.146

    4.146

    4.146

    4.146

    4.146

    4.146

    4.146

    4.147

    4.147

    4.147

    4.147

    4.147

    4.147

    4.147

    4.147

    4.147

    4.147

    4.147

    4.147

    4.147

    4.147

    4.147

    4.148

    4.148

    4.148

    4.148

    4.148

    4.148

    4.148

    4.148

    4.148

    4.148

    4.148

    4.148

    4.148

    4.148

    4.148

    4.148

    4.148

    4.149

    4.149

    4.149

    4.149

    4.149

    4.149

    4.149

    4.149

    4.149

    4.149

    4.149

    4.149

    4.149

    4.149

    4.149

    4.149

    4.15

    4.15

    4.15

    4.15

    4.15

    4.15

    4.15

    4.15

    4.15

    4.15

    4.15

    4.15

    4.15

    4.15

    4.15

    4.15

    4.15

    4.15

    4.15

    4.15

    4.151

    4.151

    4.151

    4.151

    4.151

    4.151

    4.151

    4.151

    4.151

    4.151

    4.151

    4.151

    4.151

    4.151

    4.151

    4.151

    4.151

    4.151

    4.151

    4.151

    4.151

    4.152

    4.152

    4.152

    4.152

    4.152

    4.152

    4.152

    4.152

    4.152

    4.152

    4.152

    4.152

    4.152

    4.152

    4.152

    4.152

    4.152

    4.152

    4.152

    4.152

    4.152

    4.152

    4.152

    4.153

    4.153

    4.153

    4.153

    4.153

    4.153

    4.153

    4.153

    4.153

    4.153

    4.153

    4.153

    4.153

    4.153

    4.153

    4.153

    4.153

    4.153

    4.153

    4.153

    4.153

    4.153

    4.153

    4.153

    4.154

    4.154

    4.154

    4.154

    4.154

    4.154

    4.154

    4.154

    4.154

    4.154

    4.154

    4.154

    4.154

    4.154

    4.154

    4.154

    4.154

    4.154

    4.154

    4.154

    4.154

    4.154

    4.154

    4.154

    4.154

    4.154

    4.155

    4.155

    4.155

    4.155

    4.155

    4.155

    4.155

    4.155

    4.155

    4.155

    4.155

    4.155

    4.155

    4.155

    4.155

    4.155

    4.155

    4.155

    4.155

    4.155

    4.155

    4.155

    4.155

    4.155

    4.155

    4.155

    4.155

    4.155

    4.156

    4.156

    4.156

    4.156

    4.156

    4.156

    4.156

    4.156

    4.156

    4.156

    4.156

    4.156

    4.156

    4.156

    4.156

    4.156

    4.156

    4.156

    4.156

    4.156

    4.156

    4.156

    4.156

    4.156

    4.156

    4.156

    4.156

    4.156

    4.156

    4.156

    4.156

    4.156];

    abc=nlinfit(t",v,fun,[51891 0.00083 0.00013 12050]");

    plot(t,v);hold on;

    f=@(t)(fun(abc,t));

    fplot(f,[0,50],"r")

  • 中秋節和大豐收的關聯?
  • 西紅柿怎樣施肥與管理?