# Simulink doubt -not have enough information to determine output sizes for this block

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Rakesh Jain on 28 Jul 2017
Commented: tret retret on 13 Jan 2020
Please find attached the simulink diagram. The code in the main function block is as follows :
function [xdot,xcapdot,dbar_dot,xdotr,ut] =fcn(x,xcap,dbar,xr,A,B,C,L,Kp,Kr,r,d,tau)
y=C*x
ycap=C*xcap
dbar_dot=((B'/(B'*B))*L*(y-ycap))/(tau)
xdotr=r-y
k=Kp*xcap
uf=-(k+Kr*xr)
ut=-uf-dbar
xdot=(A*x+B*ut+B*d)
xcapdot=(A*xcap)+(B*uf)+(L*(y-ycap));
On running this simulink program, I am getting the following error
Simulink does not have enough information to determine output sizes for this block. If you think the errors below are inaccurate, try specifying types for the block inputs and/or sizes for the block outputs.
Inner matrix dimensions must agree. Function 'MATLAB Function' (#35.196.200), line 16, column 11: "B*ut"
Function 'MATLAB Function' (#29.235.239), line 18, column 19:
"B*uf"
Errors occurred during parsing of MATLAB function 'MATLAB Function'
The problem lies in the fact that simulink (Refer to attached pic) is considering x and xcap and xdot as 1*1 but they are actually (3*1). How should I correct this
What error am I doing? How should I correct them.
##### 4 CommentsShowHide 3 older comments
Swarooph on 31 Jul 2017
One thing you can try is to explicitly specify the sizes for these input variables in MATLAB function block editor's Edit Data option. Take a look at the documentation example here to see how to do this and then set the size appropriately.

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### Answers (1)

Souarv De on 26 Sep 2019
Assign these values at the starting of your function
x = zeros(3,1);
xcap = zeros(3,1);
xdot = zeros(3,1);
##### 1 CommentShowHide None
tret retret on 13 Jan 2020
what is the correct way for assigning?
For example the output data is a vector [x1;x2], but the data are written to a file as [x1 x2].
If the program read out the file with
value = sscanf(file, '%g', [1,2])
and then makes a following assignment:
x1 = value(1,1)
x2 = value(1,2)
value=double([x1;x2])
I got the same error massage.
If the program makes an assignmnet as a scalar
x1 = value(1,1)
x2 = value(1,2)
value=0;
there is no error massage. But schould value be declared as a scalar?

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