AAA

curve-fittingig.m

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+clear, clc, close all
+#xf = [0:0.05:10];
+#Yf = sin (2*pi*xf/5);
+#xp = [0:10];
+#Yp = sin (2*pi*xp/5);
+#lin = interp1 (xp, Yp, xf);
+#near = interp1 (xp, Yp, xf, "nearest");
+#pch = interp1 (xp, Yp, xf, "pchip");
+#spl = interp1 (xp, Yp, xf, "spline");
+#plot (xf,Yf,"r", xf,near,"g", xf,lin,"b", xf,pch,"c", xf,spl,"m",
+#      xp,Yp,"r*");
+#legend ("original", "nearest", "linear", "pchip", "spline");
+x = [0 4 8 12];
+
+y = [5 3 10 13];
+
+n = length(x);
+
+Y = log(y);
+
+coeff = [sum(x) n; sum(x.^2) sum(x)];
+
+free = [sum(Y); sum(x.*Y)];
+
+V = coeff\free # inv(coeff) * free
+
+A = V(1)
+#exp:
+a = exp(A)
+
+b = V(2)
+
+Sr = (sum(Y - a*x - b).^2)
+
+f = a*x + b;
+
+plot(x,y,'*',x,f)
+

curvefittingig.m

@@ -0,0 +1,12 @@
+clear, clc
+xf = [0:0.05:10];
+yf = sin (2*pi*xf/5);
+xp = [0:10];
+yp = sin (2*pi*xp/5);
+lin = interp1 (xp, yp, xf);
+near = interp1 (xp, yp, xf, "nearest");
+pch = interp1 (xp, yp, xf, "pchip");
+spl = interp1 (xp, yp, xf, "spline");
+plot (xf,yf,"r", xf,near,"g", xf,lin,"b", xf,pch,"c", xf,spl,"m",
+      xp,yp,"r*");
+legend ("original", "nearest", "linear", "pchip", "spline");

differentiating-deez.m

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+clear,clc
+pkg load symbolic
+f = inline('exp(x)')
+h = 0.1;
+x = [1.4 1.5 1.6]
+y = f(x)
+first_diff_forward_y = (y(3) - y(2)) / h
+first_diff_backward_y = (y(2) - y(1)) / h
+first_diff_central_y = (y(3) - y(1)) / (2*h)
+syms x;
+Y = exp(x);
+Y1 = diff(Y)
+Y2 = diff(Y,2)
+
+YY1 = inline(Y1)
+y1e = YY1(1.5)
+YY2 = inline(Y2)
+y2e = YY2(1.5)
+M = [ first_diff_backward_y first_diff_central_y first_diff_forward_y]
+RPE = (abs(y1e - M) / y1e) * 100
+