# Getting error as Drift and volatility rates must be specified.

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vetri veeran el 18 de Nov. de 2014
Comentada: Barbara Pogacar el 12 de Mzo. de 2015
This is my code given below,
Cm=0.01; % Membrane Capcitance uF/cm^2 dt=0.04; % Time Step ms t=0:dt:25; %Time Array ms I=0.1; %External Current Applied
ENa=55.17; % mv Na reversal potential EK=-72.14; % mv K reversal potential El=-49.42; % mv Leakage reversal potential
gbarNa=1.2; % mS/cm^2 Na conductance gbarK=0.36; % mS/cm^2 K conductance gbarl=0.003 % mS/cm^2 Leakage conductance
V(1)=-60; % Initial Membrane voltage m(1)=am(V(1))/(am(V(1))+bm(V(1))); % Initial m-value n(1)=an(V(1))/(an(V(1))+bn(V(1))); % Initial n-value h(1)=ah(V(1))/(ah(V(1))+bh(V(1))); % Initial h-value
for i=1:length(t)-1
%Euler method to find the next m/n/h value m(i+1)=m(i)+dt*((am(V(i))*(1-m(i)))-(bm(V(i))*m(i))); n(i+1)=n(i)+dt*((an(V(i))*(1-n(i)))-(bn(V(i))*n(i))); h(i+1)=h(i)+dt*((ah(V(i))*(1-h(i)))-(bh(V(i))*h(i))); gNa=gbarNa*m(i)^3*h(i); gK=gbarK*n(i)^4; gl=gbarl; INa=gNa*(V(i)-ENa); IK=gK*(V(i)-EK); Il=gl*(V(i)-El);
%Euler method to find the next voltage value
V(i+1)=V(i)+(dt)*((1/Cm)*(I-(INa+IK+Il)));
end
%Store variables for graphing later FE=V; FEm=m; FEn=n; FEh=h;
clear V m n h;
Sub Functions used are given below
function a=am(v) %Alpha for Variable m a=0.1*(v+35)/(1-exp(-(v+35)/10)); end function b=bm(v) %Beta for variable m b=4.0*exp(-0.0556*(v+60)); end function a=an(v)%Alpha for variable n a=0.01*(v+50)/(1-exp(-(v+50)/10)); end function b=bn(v) %Beta for variable n b=0.125*exp(-(v+60)/80); end function a=ah(v) %Alpha value for variable h a=0.07*exp(-0.05*(v+60)); end function b =bh(v) %beta value for variable h b=1/(1+exp(-(0.1)*(v+30))); end
I am getting an error as,
Error using bm (line 140) Drift and volatility rates must be specified.
Error in fwdeuler (line 26) m(1)=am(V(1))/(am(V(1))+bm(V(1))); % Initial m-value
Please Can somebody help me to overcome this error
Thank you.
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Barbara Pogacar el 12 de Mzo. de 2015
i'm getting the same error as you for the exactly the same code!! when i made this at school it worked (windows), now i am doing report and looking at the code at home on mac, and i am getting the same error!! :) have you fixed the problem yet?
Barbara Pogacar el 12 de Mzo. de 2015
OK yes, you must rename bm...for example replace all bm with betam, or some other name, and it will work

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