Index exceeds matrix dimensions problem

I am geting '__Index exceeds matrix dimensions_' problem, while running the following function with input:

vanRijn(21,0.0005,0.002,2650,1000,0.2,0.9)

Where can my mistake be?

function [m_b]=vanRijn(T,d_50,d_90,den_s,den_w,R,v_m)

%%step1
nu=0.00000178/(1+0.0337*T+0.000221*T^2);

d_g=d_50*(9.81*(den_s-den_w)/den_w/nu^2)^(1/3);

%%step 2 Shields parameter

if d_g<=4
    theta_cr=0.24*d_g^(-1);
elseif d_g>4 && d_g<=10
    theta_cr=0.14*d_g^(-0.64);
elseif d_g>10 && d_g<=20
    theta_cr=0.04*d_g^(-0.10);
elseif d_g>20 && d_g<=150
    theta_cr=0.013*d_g^0.29;
else
    theta_cr=0.055;
end
v_cr=sqrt(theta_cr*(den_s-den_w)/den_w*9.81*d_50);

%%step 3 chezy coeficient
C_prime=18*log10(12*R/3/d_90); 

%%step 4

v_0_ef=sqrt(9.81)*v_m/C_prime;

%%Step 5
transp=(v_0_ef^2-v_cr^2)/v_cr^2;

%%step 6
m_b=0.053*(transp^2.1)/(d_g^0.3)*den_s*sqrt(9.81*(den_s-den_w)/den_w)*d_50^1.5;

[Jan]

The complete error message contains the line, which causes the error. Please consider and post such important details.

Answer 1

[Jan]

The shown code runs fine on my computer and replies 0.68863.

Did you edit the code and forgot to save? Do you have mutliple files with this name in the PATH?

which vanRijn -all

Did you create a function file called "sqrt.m" or "log10.m"? Anyhow, using the debugger with the command Fangjun has suggested already, is the best idea. Usually the debugger is even more efficient than this forum.

Just a remark:

if d_g<=4
  theta_cr=0.24*d_g^(-1);
% elseif d_g>4 && d_g<=10
elseif d_g<=10   % Better! d_g <= 4 is excluded already

Answer 2

[Fangjun Jiang]

It happens when you try to do this for example.

>> a=rand(2,3)
a =
   0.131973292606335   0.956134540229802   0.059779542947156
   0.942050590775485   0.575208595078466   0.234779913372406
>> b=a(4,5)
??? Index exceeds matrix dimensions.

Run your code step by step or type in

dbstop if error

and then run your code to find out where it happened and then why it happened.

[Meh]

thanx Fangjun 'dbstop if error' indicated me where the prob was.