Simulink with if/else and different signal dimension - matlab

I need to implement a if/else in simulink to find out if a input is a scalar value or a matrix. Please see, the diagram below :
Given:
Block(1) - is a input that can be a scalar "1" or a matrix "[[0 15];[5 10]]"
Block(2) - must return the signal dimension of the input. Ex: 1 for scalar and >1 for a matrix
The requirements are:
Everything must work interpreted or compiled (Simulink coder)
The final output of blocks (4) and (5) are scalars
I have average understanding of CMexSFunctions. So if I need to implement one to solve the problem it is ok
So far, I have had the following problems:
I don't at all if what I am planning to do is feasible
I don't know how to implement Block(2) to work on compiled mode
Even though there is a if/else, simulink performs a pre-check before running to verify if all signal dimensions are ok. During this check, it gives a error saying ex: that Block(5) has a input of matrix
Any Clues?

Block(2) is the easiest part which can be implemented using the "Probe" block in Simulink library. Your Input at port 1 must be variable sized signal since you are expecting a scalar or matrix.
I assume you are feeding Input(1) to blocks 4 and 5. At model compile time Simulink does not know which one of these blocks are going to run based on the input size. So Simulink needs to assume both blocks may get scalar or matrix. You need to make blocks 4 and 5 not throw error for both scalar and matrix even though they will be used only for one type at run-time.
If you are not able to do this, for the scalar case a simple work around is to place a Selector before block 5 that selects the first sample always. This will let Simulink know that the input to block 5 is always a scalar.

Related

Simulink - How to make transfer function block with just a zero

It's my first time using simulink and I just need it for a quick thing as part of a larger assignment.
I need to add a zero as part of controller for a feedback control system.
s+5
I'm trying to use the transfer function block but I can't enter just a numerator without a denominator. I tried the zero-pole block but it's giving errors too without poles. Is there just a zero block that I can use.
Here's the error
A time domain realization of the given zero-pole block 'untitled/Zero-Pole' failed. Check values of 'Zeros', 'Poles' and 'Gain' parameters.
Zeros: [5]
Poles: [0]
You can not use simulink to implement just a zero;numerator and denominator must have the same degree, if this condition is not realizable the system is non-causal

What are these lines doing? (Matlab)

I am trying to translate a small program from MATLAB to Python. I do not have MATLAB to run the code and see the output. Anyways, the program has a weird section that I do not know how to interpret correctly.
Here is that part of the code:
randn('state',2)
for ncase=1:3
sumex=0;
I know randn gives a matrix with normally distributed numbers - but what does it have to do with the for loop - and 'state'? I notice there is no semicolon after it.
I am guessing 'state' is the name of the matrix, and it is not initiated - nor referenced anywhere else in the code.
If I commented out randn('state',2) is it going to change the output?
Commenting out randn('state',2) will have an effect on the code and its output as randn('state',2) is old discouraged MATLAB syntax to specify the random number generator to use with randn and to seed it.
You could replace it simply with your own method to seed your own random number generator of choice in python.
for ncase=1:3 will loop from 1 to 3 in increments of 1. ncase will be 1 in the first iteration, 2 in the second iteration and 3 in the third and final iteration.
sumex=0; sets the variable sumex equal to 0.

S-function documentation that "S-function level-1 supports vector inputs and outputs. DOES NOT support multiple input and output ports"

I read in S-function documentation that "S-function level-1 supports vector inputs and outputs. DOES NOT support multiple input and output ports".
Does the second sentence mean the input and output dimension must be the same?
I have been using S-function level-1 to do the following:
[a1, b1] = choose_cells(c, d);
where a1 and b1 are outputs, c and d are inputs. All the variables are having a single value, except d is an array with 6 values.
Referring to the image attached, we all know that in S-function block, the input dimension must be SAME as output dimension, else we will get error, in this case, the input dimension is 7 while the output dimension is 2, so I have to include the "Terminator" blocks in the diagram for it to work perfectly, otherwise, I will get an error.
My problem is, when the system gets bigger, the array d could contain hundreds of variables, using this method, it means I would have to add hundreds of "Terminator" blocks in order to get this work, this definitely does not sound practical.
Could you please suggest me a wise way to implement this?
http://imgur.com/ib6BTTp
http://imageshack.us/content_round.php?page=done&id=4tHclZ2klaGtl66S36zY2KfO5co
Updated: actually I have been trying to convert my level-1 S-function to level-2 but I got stuck at calling another sub function at function Output(block) trying to look for other threads but to no avail, do you mind to provide related links?
My output depends on a lot processing with the inputs, this is the reason I need to call the sub-function in order to calculate and then return output values, all the examples that I can see are calculating their outputs directly in "function Output(block)", in my case I thought it is not possible.
I then tried to use Interpreted Matlab Function block but failed due to the output dimension is NOT the same as input dimension, also it does not support the return of more than ONE output................
Level-1 s-function supports single input and single output port. These ports must be vectors. But there is no restriction on the length. Input and output can have different lengths. You can use selector block to select only relevant data. You do not need to use Bus in the output.
There is also no restriction on calling other sub-functions from Output. If your sub-function is not in the same file it must be in the path or in the current directory.
If your MATLAB code is compatible with MATLAB Function block, I recommend using that block. It is simpler to setup and use.

For iterator (loop)

I am trying to simulate throw of the ball under angles using simulink. I'm able to simulate it for one angle but I would like to simulate it using loop. This is what I want to do in simulink using FOR :
for i=-5:10:85
Here is picture of my simulink:
If I understand your question correctly, you essentially want to rerun your simulation multiple times for different values of the constant Degrees. Instead of using a For Iterator, you may be able to achieve effectively the same result by using vector operations. That is to say, change the value of the constant Degrees from being a scalar value to instead being a vector (in this particular case just set its value to be [5:10:85]). The outputs of your Simulink model (ie the x and y results) should now be vectors corresponding to the various Degree values.
Put all the blocks into the for-iterator subsystem. The For Iterator block will output the current iteration, you can use that index (which starts at 0/1) to cycle the angle from -5 to 85 (try to hook the For Iterator block up to a Gain and Sum block). At each iteration, all the blocks in the for-iterator subsystem will run, and the output of the For Iterator block will increment by one.
The previous solution to make the angles a vector will also work.
Using MATLAB's for reference page, I'd rewrite your line as:
for i=5:10:85
...
end

keving murphy's hmm matlab toolbox assertion error

I am working on a project that needs to use hidden markov models. I downloaded Kevin Murphy's toolbox. I have some problems about the usage. In the toolbox webpage, he says that first input of dhmm_em and dhmm_logprob are symbol sequence data. On their examples, they give row vectors as data. So, when I give my symbol sequence as row vector, I get error;
??? Error using ==> assert at 9
assertion violated:
Error in ==> fwdback at 105
assert(approxeq(sum(alpha(:,t)),1))
Error in ==> dhmm_logprob at 17
[alpha, beta, gamma, ll] = fwdback(prior,
transmat, obslik, 'fwd_only', 1);
Error in ==> mainCourseProject at 110
loglik(train_act) =
dhmm_logprob(orderedSymbols,
hmm{train_act}.prior,
hmm{train_act}.trans,
hmm{act}.emiss);
However, before giving this error, code works for some symbol vectors. When I give my data as column vector, functions work fine, no errors. So why exactly am I getting this error?
You might say that I should be giving not single vectors, but vector sets, I also tried to collect my feature vectors in a struct and give row vectors as such, but nothing changed, I still get assertion error.
By the way, my symbol sequence does not have any zeros, I am doing everything almost the same as they showed in their examples, so I would be greatful if anyone could help me please.
Im not sure, but from the function call stack shown above, shouldn't the last line be hmm{train_act}.emiss instead of hmm{act}.emiss.
In other words when you computing the log-probability of a sequence, you should pass components that belong to the same HMM model (transition matrix, emission matrix, and prior probabilities).
By the way, the ASSERT in the code is a sanity check that a vector of probabilities should sum to 1. Oftentimes, when working with very small values (log-probabilities), numerical stability issues can creep in... You could edit the APPROXEQ function to relax the comparison a bit, by giving it a bigger margin of error
This error message and the code it refers to are human-readable. An assertion is a guard put in by the programmer, to ensure that certain conditions are met. In this case, what is the condition? approxeq(sum(alpha(:,t)),1) I'd venture to say that approxeq wants the values to be approximately equal, so this boils down to: sum(alpha(:,t)) ~= 1
Without knowing anything about the code, I'd also guess that these refer to probabilities. The probabilities of a node's edges must sum to one. Hopefully this starts you down a productive debugging path. If you can't figure out what's wrong with your input that produces this condition, start wading into the code a bit to see where this alpha vector comes from, and how it ended up invalid.