Rank deficient error, how to avoid it

QTU = QTU(:), HB=HB(:), P=P(:) ; 
HBinv=1./HB;
nqtu = length(QTU) ; 
U = ones(nqtu, 1) ;
M = [U P HBinv P.^2 P.*HBinv HBinv.^2]  


K = M\QTU 
QTU_modele = M*K ; 
residus = QTU-QTU_modele; 
variance_d_origine = var(QTU) ;
variance_expliquee = var(QTU_modele) ;
variance_residuelle = var(residus) ;
coefficient_correlation_r2 = variance_expliquee/variance_d_origine

[M]

Can you give more details about where does the rank deficient error appear ?

Do you have an error from Matlab ? Do you have a results that does not match what you expected ?

[Adam Danz]

1. Isolate the line that is causing the error
2. look at the values of each variable at that line and ask yourself if they make sense
3. look at the result of each operation such as a*b, a/b, a.^b and examine the output

using this method, you'll find the error. If the error still doesn't make sense, point to the exact line and the exact operation causing the error and we can help out after the problem comes into focus.

[Daniel Mbadjoun]

The error show by Matlab is:

In Modele_propre_ (line 8) % K = M\QTU
Warning: Rank deficient, rank = 5, tol =  1.996410e-05. 

K =

I obtain result of my program:

K =

     4.513991002279457e+01
     2.745762097557862e+00
    -1.766261490412594e+03
     5.146399884933867e-06
     3.632648174417475e+00
                         0


coefficient_correlation_r2 =

     9.998090847065179e-01

This result approaches the model.

The line which cause the error is:

     K= M\QTU

How can i correct the error?

[Adam Danz]

If that line is causing the error, look into the values of M and QTU.

The message you shared shows a warning, not an error.

Perhaps this will help

https://www.mathworks.com/matlabcentral/answers/49034-warning-rank-deficient-rank-0-means-what