So i want to curve fit special function ?

Hy guys i have this math function , my teacher has give me same values of rssi and d . So his assign me to curve fit this and to find the C and n values.

here is the rssi and d values:

RSSI = [ -42.11, -46.395833333333336, -48.40816326530612, -53.91836734693877, -60.52542372881356, -54.945454545454545, -55.31818181818182, -59.875, -61.36842105263158, -65.38461538461539, -64.6078431372549, -74.02564102564102, -68.86792452830188, -72.1842105263158, -72.96078431372548, -74.375 ,-72.36206896551724, -72.7 ] ;
d = [ 0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9,1,1.5,2,2.5,3,3.5,4,4.5,5];

My attemp on the matlab app costum curve fit : (So is this correct i have wtite ?)

[Torsten]

Your custom equation is wrong.

Should be

-10*n*log10(d) + C

instead of

-10*n*log(d) + C

[fiordi]

thx

Answer 1

[Matt J]

Just do an analytical fit,

RSSI = [ -42.11, -46.395833333333336, -48.40816326530612, -53.91836734693877, -60.52542372881356, -54.945454545454545, -55.31818181818182, -59.875, -61.36842105263158, -65.38461538461539, -64.6078431372549, -74.02564102564102, -68.86792452830188, -72.1842105263158, -72.96078431372548, -74.375 ,-72.36206896551724, -72.7 ] ;
d = [ 0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9,1,1.5,2,2.5,3,3.5,4,4.5,5];

p=polyfit(-10*log10(d),RSSI,1)

p = 1×2

2.0067 -61.7833

n=p(1);
C=p(2);

f=@(d) -10*n*log10(d(:))+C;

ds=linspace(0.1,5,1000);
plot(d,RSSI,'o',ds,f(ds))