Error using * Inner matrix dimensions must agree.

When i type

x2=rot*x1;

This error message appear

Error using * Inner matrix dimensions must agree.

with

rot =

         0.900736738123452          0.43436543208999
         -0.43436543208999         0.900736738123452

x1 =

     3   791
     8   388
    10   570
    17   285
    24   836
    32   342
    35   656
    43   339
    44   634
    53   656
    55   445
    57   657
    59   179
    60    62
    62   217
    64   618
    73   629
    74   629
    77   617
    84   867
   126   401
   133   920
   138    82
   141   386
   158   528
   168    65
   184   660
   191   650
   198    13
   208   537
   219   730
   224   524
   227   527
   230   957
   233   955
   236   954
   253    89
   253   917
   258   964
   263   836
   275   478
   285   622
   289   240
   292   418
   295   747
   297   748
   297   946
   299   782
   311   395
   317   777
   318   105
   322   166
   326   792
   355   927
   360   103
   372   853
   384   110
   387   534
   387   574
   391   421
   398   579
   404   702
   419   324
   422   323
   424   374
   425   908
   435   101
   443    30
   464   761
   468   899
   470   897
   471   494
   475   754
   488   888
   496   707
   496   799
   505   565
   506   567
   513   551
   517   878
   523   531
   528   460
   542   187
   555   210
   558   449
   572   404
   576   403
   577   597
   583   397
   588   711
   592   245
   595   873
   596    83
   621     4
   621   900
   627   692
   650   559
   654   558
   656   870
   663    83
   665   444
   665   665
   666   412
   669   155
   669   552
   672   361
   673   359
   673   485
   680   660
   685   486
   694   352
   695   711
   698   650
   709   231
   712   624
   728   435
   731   891
   732   309
   733    81
   737   421
   737   425
   742    53
   743    51
   746   839
   747   842
   752   347
   753    84
   755   879
   771     9
   776   328
   778   395
   829   338
   829   340
   836   333
   853   324
   863   370
   913   581
   917   644
   926   455
   936   396
   943   741
   949   609
   949   620
   954   332
   959   169
   966   329
   967   327
   972   725

Can any one help me

to solve this problem

please!

thx

Answer 1

[the cyclist]

When you do a matrix multiplication A*B, the number of columns of A must be equal to the number of rows of B. That is basic matrix algebra.

[Walter Roberson]

You might be able to use

rot * x1'

Answer 2

[alejandro hernandez]

clear all
T=0.1;
L=0/4;
L1=1/4;
L2=2/4;
L3=3/4;
L4=1;
A=[0 1;0 0];
I=[1 0;0 1];
B=[0 0;0 1];

M=10;

x=[1 1];
for i=2:M
   x(i+1)=(T/L)*(A)-(1/L)+2*(I)*x+(T/L)*(B)*(2)+(1/L)*(I)-1*x;
end

Error using  * 
Inner matrix dimensions must agree.

Error in centrales_ponderadas (line 16)
   x(i+1)=(T/L)*(A)-(1/L)+2*(I)*x+(T/L)*(B)*(2)+(1/L)*(I)-1*x;

[Walter Roberson]

Did you notice that you have a number of divisions by 0? You are dividing by L and L is 0.

[Walter Roberson]

In the sub-expression 2*(I)*x, I is 2 by 2, and x is 1 x 2 to start, so I*x is a 2 x 2 * 1 x 2 which is not permitted because the inner dimensions do not match.

Your T and L are scalars and your A is 2 x 2, so (T/L)*A is scalar * 2 x 2 which is going to give you 2 x 2, so we know that the rest of the added terms are intended to give a 2 x 2 result. Your 2*(I)*x term must give a 2 x 2 result to match the (T/L)*A term.

But suppose that you managed to do that, and suppose the rest of the terms matched in size. Then the result would be 2 x 2, and you would be trying to assign that 2 x 2 value into the single location x(i+1)

If you manage to select a single element out to store into x(i+1) then x is going to become one element longer. That is important when you reach the 2*(I)*x in the next iteration: it will be a larger result than in the previous iteration and that makes it even less likely that you could correctly select out the one single value from the expression to store into x(i+1) that round.

Answer 3

[rana vijay singh fezah]

t = 0:0.01:10;
>> u = 9.7*t + pi/2;
>> y = exp(-8*t) *sin(u);
Error using  * 
Inner matrix dimensions must agree.

>> y = exp(-8*t) * sin(u);
Error using  * 
Inner matrix dimensions must agree.

CAN SOMEONE SOLVE THIS!!!!

[Walter Roberson]

• is algebraic matrix multiplication in MATLAB. For A*B, size(A,2) must equal size(B,1) -- columns of the first must equal rows of the second, with the result being size(A,1) by size(B,2)

You want element-by-element multiplication, which is .* instead of *

exp(-8*t) .* sin(u)

Answer 4

[Cristian Rosca]

if i have

>> a=-pi/2;

>> b=3*pi/2;

>> N=7;

>> h=(b-a)/(N-1);

>> x=a:h:b;

>> y=(x.^2)*log(abs(x)+1)*xcos(x);

Error using *

Inner matrix dimensions must agree.