diff --git a/doc/variable.html b/doc/variable.html index 366b507755..a337aecfd7 100644 --- a/doc/variable.html +++ b/doc/variable.html @@ -28,10 +28,11 @@ equal or atom args = one formula containing numbers, thermo keywords, math operations, group functions, atom values and vectors, compute/fix/variable references numbers = 0.0, 100, -5.4, 2.8e-4, etc thermo keywords = vol, ke, press, etc from thermo_style - math operations = (), -x, x+y, x-y, x*y, x/y, x^y, - sqrt(x), exp(x), ln(x), log(x), - sin(x), cos(x), tan(x), asin(x), acos(x), atan(x), - ceil(x), floor(x), round(x) + math operators = (), -x, x+y, x-y, x*y, x/y, x^y, + x==y, x!=y, xy, x>=y + math functions = sqrt(x), exp(x), ln(x), log(x), + sin(x), cos(x), tan(x), asin(x), acos(x), atan(x), + ceil(x), floor(x), round(x) group functions = count(group), mass(group), charge(group), xcm(group,dim), vcm(group,dim), fcm(group,dim), bound(group,xmin), gyration(group), ke(group) @@ -239,13 +240,15 @@ valid (though strange) variable formula: 
variable x equal "pe + c_MyTemp / vol^(1/3)"

Specifically, an formula can contain numbers, thermo keywords, math -operations, group functions, atom values, atom vectors, compute -references, fix references, and references to other variables. +operators, math functions, group functions, region functions, atom +values, atom vectors, compute references, fix references, and +references to other variables.

- + + @@ -280,19 +283,34 @@ evaluated directly in an input script (not during a run), then the values accessed by the thermo keyword must be current. See the discussion below about "Variable Accuracy".

-

Math operations are written in the usual way, where the "x" and "y" in +

Math operators are written in the usual way, where the "x" and "y" in the examples above can be another section of the formula. Operators -are evaluated left to right and have the usual precedence: unary minus -before exponentiation ("^"), exponentiation before multiplication and -division, and multiplication and division before addition and -subtraction. Parenthesis can be used to group one or more portions of -a formula and enforce a desired order of operations. Additional math -operations can be specified as keywords followed by a parenthesized -argument, e.g. sqrt(v_ke). Note that ln() is the natural log; log() -is the base 10 log. The ceil(), floor(), and round() operations are -those in the C math library. Ceil() is the smallest integer not less -than its argument. Floor() if the largest integer not greater than -its argument. Round() is the nearest integer to its argument. +are evaluated left to right and have the usual C-style precedence: +unary minus before exponentiation ("^"); exponentiation before +multiplication and division; multiplication and division before +addition and subtraction; addition and subtraction before the 4 +relational operators "<", "<=", ">", and ">="; and those 4 relational +operators before the remaining two relational operators "==" and "!=". +Parenthesis can be used to group one or more portions of a formula and +enforce a different order of evaluation than that invoked by the the +default precedence. +

+

The 6 relational operators return either a 1.0 or 0.0 depending on +whether the relationship between x and y is true or false. For +example the expression x<10.0 in an atom-style variable formula will +return 1.0 for all atoms whose x-coordinate is less than 10.0, and 0.0 +for the others. This can be used as a masking or selection operation +in a formula. For example, the number of such atoms could be +calculated by taking the returned per-atom vector of ones and zeroes +and passing it to the compute reduce command. +

+

Math functions can be specified as keywords followed by a +parenthesized argument, e.g. sqrt(v_ke). Note that ln() is the +natural log; log() is the base 10 log. The ceil(), floor(), and +round() operations are those in the C math library. Ceil() is the +smallest integer not less than its argument. Floor() if the largest +integer not greater than its argument. Round() is the nearest integer +to its argument.

Group functions take one or two arguments in a specific format. The first argument is the group-ID. The dim argument, if it exists, is diff --git a/doc/variable.txt b/doc/variable.txt index c5ab16b8fa..dc8063fa5f 100644 --- a/doc/variable.txt +++ b/doc/variable.txt @@ -23,10 +23,11 @@ style = {delete} or {index} or {loop} or {world} or {universe} or {uloop} or {eq {equal} or {atom} args = one formula containing numbers, thermo keywords, math operations, group functions, atom values and vectors, compute/fix/variable references numbers = 0.0, 100, -5.4, 2.8e-4, etc thermo keywords = vol, ke, press, etc from "thermo_style"_thermo_style.html - math operations = (), -x, x+y, x-y, x*y, x/y, x^y, - sqrt(x), exp(x), ln(x), log(x), - sin(x), cos(x), tan(x), asin(x), acos(x), atan(x), - ceil(x), floor(x), round(x) + math operators = (), -x, x+y, x-y, x*y, x/y, x^y, + x==y, x!=y, xy, x>=y + math functions = sqrt(x), exp(x), ln(x), log(x), + sin(x), cos(x), tan(x), asin(x), acos(x), atan(x), + ceil(x), floor(x), round(x) group functions = count(group), mass(group), charge(group), xcm(group,dim), vcm(group,dim), fcm(group,dim), bound(group,xmin), gyration(group), ke(group) @@ -233,12 +234,14 @@ valid (though strange) variable formula: variable x equal "pe + c_MyTemp / vol^(1/3)" :pre Specifically, an formula can contain numbers, thermo keywords, math -operations, group functions, atom values, atom vectors, compute -references, fix references, and references to other variables. +operators, math functions, group functions, region functions, atom +values, atom vectors, compute references, fix references, and +references to other variables. Number: 0.2, 100, 1.0e20, -15.4, etc Thermo keywords: vol, pe, ebond, etc -Math operations: (), -x, x+y, x-y, x*y, x/y, x^y, sqrt(x), exp(x), ln(x), log(x), sin(x), cos(x), tan(x), asin(x), acos(x), atan(x), ceil(x), floor(x), round(x) +Math operators: (), -x, x+y, x-y, x*y, x/y, x^y, x==y, x!=y, xy, x>=y +Math functions: sqrt(x), exp(x), ln(x), log(x), sin(x), cos(x), tan(x), asin(x), acos(x), atan(x), ceil(x), floor(x), round(x) Group functions: count(ID), mass(ID), charge(ID), xcm(ID,dim), \ vcm(ID,dim), fcm(ID,dim), bound(ID,dir), gyration(ID), ke(ID) Region functions: count(ID,IDR), mass(ID,IDR), charge(ID,IDR), xcm(ID,dim,IDR), \ @@ -275,19 +278,34 @@ evaluated directly in an input script (not during a run), then the values accessed by the thermo keyword must be current. See the discussion below about "Variable Accuracy". -Math operations are written in the usual way, where the "x" and "y" in +Math operators are written in the usual way, where the "x" and "y" in the examples above can be another section of the formula. Operators -are evaluated left to right and have the usual precedence: unary minus -before exponentiation ("^"), exponentiation before multiplication and -division, and multiplication and division before addition and -subtraction. Parenthesis can be used to group one or more portions of -a formula and enforce a desired order of operations. Additional math -operations can be specified as keywords followed by a parenthesized -argument, e.g. sqrt(v_ke). Note that ln() is the natural log; log() -is the base 10 log. The ceil(), floor(), and round() operations are -those in the C math library. Ceil() is the smallest integer not less -than its argument. Floor() if the largest integer not greater than -its argument. Round() is the nearest integer to its argument. +are evaluated left to right and have the usual C-style precedence: +unary minus before exponentiation ("^"); exponentiation before +multiplication and division; multiplication and division before +addition and subtraction; addition and subtraction before the 4 +relational operators "<", "<=", ">", and ">="; and those 4 relational +operators before the remaining two relational operators "==" and "!=". +Parenthesis can be used to group one or more portions of a formula and +enforce a different order of evaluation than that invoked by the the +default precedence. + +The 6 relational operators return either a 1.0 or 0.0 depending on +whether the relationship between x and y is true or false. For +example the expression x<10.0 in an atom-style variable formula will +return 1.0 for all atoms whose x-coordinate is less than 10.0, and 0.0 +for the others. This can be used as a masking or selection operation +in a formula. For example, the number of such atoms could be +calculated by taking the returned per-atom vector of ones and zeroes +and passing it to the "compute reduce"_compute_reduce.html command. + +Math functions can be specified as keywords followed by a +parenthesized argument, e.g. sqrt(v_ke). Note that ln() is the +natural log; log() is the base 10 log. The ceil(), floor(), and +round() operations are those in the C math library. Ceil() is the +smallest integer not less than its argument. Floor() if the largest +integer not greater than its argument. Round() is the nearest integer +to its argument. Group functions take one or two arguments in a specific format. The first argument is the group-ID. The {dim} argument, if it exists, is

Number 0.2, 100, 1.0e20, -15.4, etc
Thermo keywords vol, pe, ebond, etc
Math operations (), -x, x+y, x-y, x*y, x/y, x^y, sqrt(x), exp(x), ln(x), log(x), sin(x), cos(x), tan(x), asin(x), acos(x), atan(x), ceil(x), floor(x), round(x)
Math operators (), -x, x+y, x-y, x*y, x/y, x^y, x==y, x!=y, xy, x>=y
Math functions sqrt(x), exp(x), ln(x), log(x), sin(x), cos(x), tan(x), asin(x), acos(x), atan(x), ceil(x), floor(x), round(x)
Group functions count(ID), mass(ID), charge(ID), xcm(ID,dim), vcm(ID,dim), fcm(ID,dim), bound(ID,dir), gyration(ID), ke(ID)
Region functions count(ID,IDR), mass(ID,IDR), charge(ID,IDR), xcm(ID,dim,IDR), vcm(ID,dim,IDR), fcm(ID,dim,IDR), bound(ID,dir,IDR), gyration(ID,IDR), ke(ID,IDR)
Atom values mass[i], type[i], x[i], y[i], z[i], vx[i], vy[i], vz[i], fx[i], fy[i], fz[i]