Provided by: minc-tools_2.3.00+dfsg-3build2_amd64 
NAME
minccalc - perform complex math operations on minc files
SYNOPSIS
mincalc [<options>] <in1>.mnc [<in2>.mnc...] <out>.mnc
DESCRIPTION
Minccalc will perform complex, voxel-by-voxel math operations, on one or more minc files of the same
shape and having the same coordinate sampling, producing a single output file. The operations to be
performed are input using the -expression argument (see EXPRESSIONS). By default, the output file is the
last non-option argument. However, if the -outfile option is used, then all non-option arguments are
considered input files and the output file names come from the -outfile options, of which there can be
more than one.
OPTIONS
Note that options can be specified in abbreviated form (as long as they are unique) and can be given
anywhere on the command line.
-2 Create MINC 2.0 format output files.
-help Print summary of command-line options and exit.
-version
Print the program's version number and exit.
-clobber
Overwrite an existing file.
-noclobber
Don't overwrite an existing file (default).
-no_clobber
Synonym for -noclobber.
-verbose
Print out progress information for each chunk of data copied (default).
-quiet Do not print out progress information.
-debug Print out debugging information.
-copy_header
Copy all of the header information from the first input file (default for one input file).
-nocopy_header
Do not copy all of the header from the first input file; copy only coordinate information (default
for more than one input file).
-filetype
Create an output file with the same type as the first input file (default).
-byte Store output voxels in 8-bit integer format.
-short Store output voxels in 16-bit integer format.
-int Store output voxels in 32-bit integer format.
-long Superseded by -int.
-float Store output voxels in 32-bit floating point format.
-double
Store output voxels in 64-bit floating point format.
-signed
Use signed, two's complement integer format. Applies only if the output voxel type is specified to
be an integer type (one of -byte, -short, -int or -long).
-unsigned
Use unsigned integer format. Applies only if the output voxel type is specified to be an integer
type (one of -byte, -short, -int or -long).
-range min max
Restrict the valid range of integer data. Applies only if one of the -byte, -short, -int or -long
options is specified.
-max_buffer_size_in_kb size
Specify the maximum size of the internal buffers (in kbytes). Default is 4096 (4MB).
-dimension dimname
Specify a dimension along which we wish to perform a cumulative operation.
-check_dimensions
Check that all input files have matching sampling in world dimensions (default).
-nocheck_dimensions
Ignore any differences in world dimensions sampling for input files.
-propagate_nan
For cumulative vector operations (sum, prod and avg), invalid data (Not-A-Number or NaN) in any
element of the vector will produce invalid data in the result (default).
-ignore_nan
For cumulative vector operations, invalid data (NaN) in the vector is ignored, ie. treated as
though it is not present.
-nan When an illegal operation is attempted at a voxel (such as divide by zero), the result is invalid
data (NaN) (default). Having no valid input data for a cumulative operation is also considered an
illegal operation when -ignore_nan is used.
-zero When an illegal operation is attempted at a voxel (such as divide by zero), the result is value
zero.
-illegal_value value
When an illegal operation is attempted at a voxel (such as divide by zero), the result is the
value specified by this option.
-expression string
Specify the expression to evaluate at each voxel (see EXPRESSIONS).
-expfile filename
Specify a file containing an expression to evaluate at each voxel (see EXPRESSIONS). If filename
``-'' is given, then the expression is read from stdin. The only difference from command-line
expressions is that comments can be given in the file. A comment line is specified by placing a
``#'' as the first non-whitespace character of the line. Minccalc scripts can be created by
setting the first line to
#! /usr/local/mni/bin/minccalc -expfile
-outfile symbol output-file
Specify that output should be written to the specified file, taking values from the symbol which
should be created in the expression (see the EXAMPLES section). If this option is given, then all
non-option arguments are taken as input files. This option can be used multiple times for multiple
output files.
-eval_width value
Specify the number of voxels to process in parallel. Default is 200.
EXPRESSIONS
The -expression argument is a single string that describes the function to evaluate. The function
expression is typically written in terms of the vector A.
For example, the following expression will sum the first two input files together:
A[0] + A[1]
Multiple expressions can be given separated by semicolons, in which case only the value of the last
expression is used. These expression lists can be used with assignment expressions to make the syntax
very C-like:
ratio = A[0]/A[1]; A[2]*exp(-ratio)
An expression list in curly brackets is a valid expression and returns the value of last expression in
the list. This is particularly useful in for and if expressions (see below).
There are two types of values in the language: vectors and scalars. Scalars literals are floating point
numbers or may appear as symbols whose name starts with a lowercase letter.
Besides normal scalar operators such as +, -, * and /, the expression language also supports the infix
exponentiation operator ^ , the usual relational operators <, <=, >, >=, ==, != as well as the boolean
operators && (and), || (or) and ! (not). Note that the && and || boolean operators always evaluate both
operands, unlike C. Scalar mathematical functions include abs, sqrt, exp, log, sin, cos, tan, asin, acos
and atan. There are also some specialized functions:
isnan(v) - 1 if v is invalid and 0 otherwise
clamp(v1,v2,v3) - v1 bounded by [v2, v3]
segment(v1,v2,v3) - tests if v1 is in [v2, v3]
The scalar constant NaN is defined such that isnan(NaN) return 1.
Vectors can be written in the following `extensional' form
[ value1, value2, ... ]
or by using the following range-generating notations:
[ a : b ] generates {a, a+1, ..., b-1, b}
[ a : b ) generates {a, a+1, ..., b-1}
( a : b ] generates {a+1, ..., b-1, b}
( a : b ) generates {a+1, ..., b-1}
or be generated, by `intension'. The following intension expression generates the vector {3,2,1}:
{ i in [1:3] | 4 - i }
Vectors may also appear as symbols whose name starts with an uppercase letter.
In addition to the scalar operators, the following vector operators are supplied:
avg - the average value of the scalars in vector
len - the length of
sum - the sum of the elements of
prod - the product of the elements of
max - the maximum value of
min - the minimum value of
imax - the index of the maximum value of
imin - the index of the minimum value of
V[s] - the s'th element of vector V with origin 0.
Symbol names are introduced into a global symbol table by assignment expressions of the form
a = A[2] * log(2)
Symbols starting with a lowercase letter represent scalars while those starting with an uppercase letter
represent vectors. Since = is an operator, its result can be used in an expression (as in C).
A few control constructs are provided:
For loops can be created to loop over a vector, assigning each value to a symbol and then evaluating an
expression. This is done with expressions of the form
total=0; for{i in [0:len(A))} total=total+A[i]; total
which is equivalent to sum(A). Note that this is similar to using
total=0; len{i in [0:len(A)) | total=total+A[i]}; total
since the for construct is actually an operator (although it is usually only used for changing symbol
values). Note also that without the final "total", the expression would not be very useful since it would
only return the length of the vector.
As in C, a list of expressions can be specified in curlies:
total=total2 = 0;
for {i in [0:len(A))} {
total = total + A[i];
total2 = total2 + A[i]^2
}
There are also a few forms of the if-then-else construct:
A[0]<0 ? 0 : A[0]
if (A[0]<0) result=0 else result=A[0]
The else is optional. Again, the if construct is an operator, and the then or else expressions can be
expression lists in curlies, in which case the value of the last expression is returned. If the else
expression is missing, then the value 0 is returned when the test expression is 0 (false).
The principal oddity with the for and if constructs is that unlike C statements, they must be separated
from the next expression by a semicolon even when an expression list in curlies is used:
for i in [0:len(A)) {total=total+A[i]} ; total/len(A)
if (A[i]>0) {result=2;} else {result=1} ; result*5
An alternative way to introduce symbol names is through let-expressions. For example, the following
expression will always evaluate to 3:
let a = 1, b = 2 in a + b
These were originally designed to create variables only within the evaluated expression, but
modifications have been made so that the global symbol table is changed.
EXAMPLES
Here is an expression for calculating standard deviation, taking into account the possibility of invalid
input data, which is ignored:
s0 = s1 = s2 = 0;
for { i in [0:len(A)) } {
v=A[i];
if (!isnan(v)) {
s0 = s0 + 1;
s1 = s1 + v;
s2 = s2 + v*v;
}
};
if (s0 > 1) {
sqrt((s2 - s1*s1/s0) / (s0-1));
}
else {
NaN;
};
The last if could be changed to return 0 if s0 is > 0 but <= 1. We also drop the curly brackets, but then
there must not be a ";" between the if and the else
if (s0 > 1)
sqrt((s2 - s1*s1/s0) / (s0-1))
else if (s0 > 0)
0
else
NaN
If we want both the mean and the standard deviation, we can use the -outfile option, invoking the command
with
minccalc -expfile stdev \
-outfile mean mean.mnc \
-outfile stdev stdev.mnc \
infile1.mnc infile2.mnc ...
And using the expression file (with yet another form of if expression):
s0 = s1 = s2 = 0;
for {i in [0:len(A))} {
v=A[i];
if (!isnan(v)) {
s0 = s0 + 1;
s1 = s1 + v;
s2 = s2 + v*v;
}
};
stdev = (s0 > 1) ? sqrt((s2 - s1*s1/s0) / (s0-1)) :
(s0 > 0) ? 0 : NaN ;
mean = (s0 > 0) ? s1 / s0 : NaN ;
CAVEATS
A few things you should remember...
Vector variables must start with an uppercase letter.
Vector variable names must not be one of the function keywords,
sum, len, prod, ... etc
For loops and if expressions always need to be separated from the next expression by a semicolon.
The symbol table is global.
Boolean operators && and || always evaluate both operands.
A note on parallelism: For efficiency reasons, evaluations are done on many voxels at once (the number of
voxels is referred to as the width of the evaluation and is changed with the -eval_width option). An odd
consequence of this is that both sides of an if-else statement are always evaluated (unless all voxels
give the same test result), but statements within each consequent are only evaluated on the appropriate
voxels. In particular, entries in the symbol table are only modified according to a voxel mask. A side-
effect of this is that any vector symbol set in an if-else consequent must not change the length of the
symbol (although it can create it) and both sides of the consequent must agree on the length of any
vector symbols that they both modify. If this is not clear, just try it - the program will complain if it
is not happy.
AUTHOR
Andrew Janke - a.janke@gmail.com
COPYRIGHTS
Copyright © 2000 by Andrew Janke
SEE ALSO
mincmath(1)
$Date: 2008-01-11 04:24:16 $ MINCCALC(1)