Matlab linearize a characteristic curve?

What do you need a tool for? You just trace the above relationship to T.

t=[0:2:100]
T = t + 273.15
Rn=580
Tn=298.15
B= sqrt(26+5)*100
arg=(1./T-1./Tn)*B
R = exp(arg)*Rn
plot(t,R);
xlabel('T [°C]') 
ylabel('R [\Omega]')
title('NTC Linearisierung')
hold on;
t50 = 50;
T50 = t50 + 273.15;
R50 = exp((1./T50-1./Tn)*B)*Rn
dRdT50 = -R50*B/T50^2;
Rlin = R50+(t-t50)*dRdT50;
plot(t,Rlin);
plot(50,R50,'o')
hold on
legend('Kennlinie','Linearisierung um 50°C', '50°')
grid on;