incl/Matlab.R

In HenrikBengtsson/R.matlab: Read and Write MAT Files and Call MATLAB from Within R

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# This example will try to start the MATLAB server on the local machine,
# and then setup a Matlab object in R for communicating data between R
# and MATLAB and for sending commands from R to MATLAB.
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# 1.  Load R.matlab
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library(R.matlab)


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# 2.  Start MATLAB
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# 2.1.  Start MATLAB from R?
# Start MATLAB server on the local machine (if this fails, 
# see help(Matlab) for alternatives).
Matlab$startServer()

# 2.2.  OR start MATLAB externally,
#       THEN add 'externals' subdirectory to the MATLAB path

#  (Where is the 'externals' subdirectory?)
print(system.file("externals", package = "R.matlab"))

#       THEN from within MATLAB,
#            issue MATLAB command "MatlabServer"
# Note: If issued from a MATLAB command line, this last command
#       prevents further MATLAB 'command line' input
#       until something like close(matlab) at the end of this script

# 2.3.  If both these options fail, see help(Matlab) for alternatives.


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# 3. Create a MATLAB client object used to communicate with MATLAB
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matlab <- Matlab()

# 3.1 Check status of MATLAB connection (not yet connected)
print(matlab)

# 3.2 If you experience any problems, ask for detailed outputs
#     by uncommenting the next line
# setVerbose(matlab, -2)

# 3.3 Connect to the MATLAB server.
isOpen <- open(matlab)

# 3.4 Confirm that the MATLAB server is open, and running
if (!isOpen)
  throw("MATLAB server is not running: waited 30 seconds.")

# 3.5 Check status of MATLAB connection (now connected)
print(matlab)


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# 4.  Sample uses of the MATLAB server
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# 4.1 Run MATLAB expressions on the MATLAB server
evaluate(matlab, "A = 1+2;", "B = ones(2, 20);")

# 4.2 Ask MATLAB to display a value (without transferring it to R)
evaluate(matlab, "A")

# 4.3 Get MATLAB variables
data <- getVariable(matlab, c("A", "B"))
cat("Received variables:\n")
str(data)

# 4.4 Set variables in MATLAB
ABCD <- matrix(rnorm(10000), ncol = 100)
str(ABCD)
setVariable(matlab, ABCD = ABCD)

# 4.5 Retrieve what we just set
data <- getVariable(matlab, "ABCD")
cat("Received variables:\n")
str(data)

# 4.6 Create a function (M-file) on the MATLAB server
setFunction(matlab, "            \
  function [win, aver] = dice(B) \
  %Play the dice game B times    \
  gains = [-1, 2, -3, 4, -5, 6]; \
  plays = unidrnd(6, B, 1);      \
  win = sum(gains(plays));       \
  aver = win/B;                  \
")

# 4.7 Use the MATLAB function just created
evaluate(matlab, "[w, a] = dice(1000);")
res <- getVariable(matlab, c("w", "a"))
print(res)


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# 5. Exception handling
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# 5.1 Try to get non-existing MATLAB variable
#     (will result in an informative error)
tryCatch({
  data <- getVariable(matlab, "unknown")
  cat("Received variables:\n")
  str(data)
}, error = function(ex) {
  print(ex)
})
# Confirm that things still work
data <- getVariable(matlab, "A")
cat("Received variables:\n")
str(data)


# 5.2 Try to evaluate a MATLAB expression that fails
#     (will result in an informative error)
tryCatch({
  res <- evaluate(matlab, "C = 1+unknown;")
  res
}, error = function(ex) {
  print(ex)
})
# Confirm that things still work
res <- evaluate(matlab, "C = 1+2;")
print(res)
data <- getVariable(matlab, "C")
cat("Received variables:\n")
str(data)


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# 6.  Done:  close the MATLAB client
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# When done, close the MATLAB client, which will also shutdown
# the MATLAB server and the connection to it.
close(matlab)

# 6.1 Check status of MATLAB connection (now disconnected)
print(matlab)