I'm new to coffeescript. Is there a way to take these three lines setting the rotation and accomplish the same thing, like you would do in python by unpacking a tuple?
#cosines = [0,1,0]
#branch.rotation.x = Math.asin(#cosines.x)
#branch.rotation.y = Math.asin(#cosines.y)
#branch.rotation.z = Math.asin(#cosines.z)
This is the best code I could come up with.
#cosines = [0,1,0]
rot = #branch.rotation
[rot.x, rot.y, rot.z] = [Math.asin(c) for c in #cosines]
The unpacking destructuring is the same as in Python, but with square brackets.
Related
I am looking for some style/best practice advice. I often find myself writing scripts which need many (several tens of) parameters to be defined at the beginning. Then these parameters are used by many functions within the script. A minimum, simplified example might look something like the following:
params.var1 = 1;
params.var2 = 10;
params.var3 = 100;
params.var4 = 1e3;
result1 = my_func1(params);
result2 = my_func2(params);
Now, I don't want to pass many inputs into every function, so am reluctant to do something like result1 = my_func1(var1,var2,var3,var4,...). Therefore, I always find myself making each variable a field of a structure (e.g. params), and then passing this structure alone into each function, as above. The structure is not modified by the functions, only the parameters are used for further calculations.
One of the functions might look like this then:
function result = my_func1(params)
var1 = params.var1;
var2 = params.var2;
var3 = params.var3;
var4 = params.var4;
result = var1.^2 + var2.^2 -var3.^3 + var4;
end
Now, because I don't want to refer to each variable within the function as params.var1, etc. (in the interest of keeping the expression for result as clear as possible), I first do all this unpacking at the beginning using var1 = params.var1.
I suppose the best thing to be doing in situations like this might be to use classes (because I have some data and also want to perform functions on that data). Are there any better ways for me to be doing this kind of thing without moving fully to object-oriented code?
I would simply leave the unpacking out. Call the struct params something shorter inside the function, to keep clutter to a minimum:
function result = my_func1(p)
result = p.var1.^2 + p.var2.^2 - p.var3.^3 + p.var4;
end
I would keep calling it params elsewhere, so you don’t have to deal with cryptic names.
You can define constant functions:
function out = var1
out = 1;
end
function out = var2
out = 10;
end
function result = my_func1
result = var1.^2 + var2.^2;
end
Based on your actual application you may pass array of numbers:
var = [var1 var2 var3 var4];
my_func1(var);
my_func1(var1,var2,var3,var4,...) in my opinion is preferred over passing struct.
my Problem is the following:
I have about 300 Struct files given.
They are set up like this:
DSC_0001 has about 250 other struct files in it:
-> like this: DSC_0001.marker_1
And this one has 10 Numbers in it.
Like that:
DSC_0001.marker_1.flow_angle = 90
and now I want to iterate through all the Struct files
Something like that:
for i = 1:300
for j = 1:250
flow_angle = DSC_**i**.marker_**j**
end
end
Is there a way to do this?
I have the feeling that it could be really easy but I just can't find the solution...
I hope my question is clear enough...
Thanks for your help!
If possible don't use eval.
It depends on how your data is stored, but one possiblity is that it is in a .mat file. In that case it can be loaded using
DSC_structs = load('My_DSC_struct_file.mat');
and then you can access the values like so:
for i = 1:300
for j = 1:250
flow_angle(i,j) = DSC_structs.(['DSC_' sprintf('%04d',i)]).(['marker_' sprintf('%d',j)]);
end
end
Why avoid the eval function
Edit: You say that each struct is in a different file. That's a bit messier. I would probably do something like this to load them:
DSC_structs = cell(1,300);
for i = 1:300
%Note: I'm guess at your file names here
DSC_structs{i} = load(['DSC_' sprintf('%04d',i) '.mat'];
end
and then access the values as
DSC_structs{i}.(['DSC_' sprintf('%04d',i)]).(['marker_' sprintf('%d',j)]);
I guess this is a use case for the dreaded eval function:
for i = 1:300
for j = 1:250
eval (['flow_angle = DSC_', sprintf('%04d',i), '.marker_', num2str(j)]);
end
end
BUT NB there are 2 problems with my code above
You haven't told us where you want to store your angle, so my code doesn't :/ but you'd want something like this if you just want to store them in a matrix: eval (['flow_angle(', num2str(i), ',', num2str(j), ') = DSC_', sprintf('%04d',i), '.marker_', num2str(j)])
eval is a horrible way of doing things but you're forced to because someone saved your data in a horrible. Sort yourself out now for the future by re-saving your data in a smarter way! so something like:
.
for i = 1:300
eval ( ['DSC(', num2str(i), ') = DSC_', sprintf('%04d',i)]);
end
%// then save DCS!
And now your can iterate through this matrix of structs rather than having a 300 structs polluting your workspace and forcing you to use eval
I have a huge cell vector cc (size: 1xN) of the form:
cc{1} = {'indexString1', 'str_row1col1', 'str_row1col2' }
cc{2} = {'indexString2', 'str_row2col1', 'bighello', 'str_row1col3' }
cc{3} = {'indexString3','str_row3col1'}
cc{4} = {'indexString4','str_row3col1', 'helloWorld'}
I want to traverse each cell and remove specific cells that contain the word "hello", e.g c{4}{2}. Can we do that without for loops keeping the final structure of cc?
Best,
Thoth.
EDIT: From the answers and comments I have seen that the structure of the cell impose some limitations. So any other suggestion to store my data are welcome. I just want to keep together all the cells (e.g. 'str_row1col1', 'str_row1col2') that correspond to the same indexString*n* (e.g. indexString1). I made this edit in case it helps some final reshape.
Using regular expressions, you can obtain a logical array in which zeros represent occurences of the word 'hello' somewhere in the nested cell. As #LuisMendo pointed out, this would be much easier to delete the unwanted cells if they were not nested:
clc
clear
cc{1} = {'str_row1col1', 'str_row1col2' };
cc{2} = {'str_row2col1', 'bighello', 'str_row1col3' };
cc{3} = {'str_row3col1'};
cc{4} = {'str_row3col1', 'helloWorld'};
A = (cellfun(#isempty,regexp([cc{:}],'(\w*hello|hello\w*)','match')))
Gives the following array:
A =
1 1 1 0 1 1 1 0
For the rest I think you would need a loop since the nested cells are not all of the same size. Anyhow I hope it helps you a bit.
EDIT Here is what you can do using a for loop. In order to identify words of interest (earth and water as in your comment below), simply add them to the argument in the call to regexp. This character: | is used to make some sort of list so that Matlab checks all the expressions in the brackets.
Please refer to this page for more infos on regular expressions. There is also a possibility to look for regular expressions with case-sensitivity.
Sample code, in which I added strings containing earth and water:
cc{1} = {'str_row1col1', 'earth!superman' 'str_row1col2' 'DummyString'};
cc{2} = {'str_row2col1', 'bighello', 'str_row1col3' };
cc{3} = {'str_row3col1' 'str_row3col3' 'water_batman'};
cc{4} = {'str_row3col1' 'str_row4col2' 'helloWorld'};
cc{5} = {'str_row5_LegoMan' 'str_row5col2' 'AnotherDummyString' 'Useless String' 'BonjourWorld'};
% With a for loop, for example:
FinalCell = cell(size(cc,2),1);
for k = 1:size(cc,2)
DummyCell = cc{k}; % Use dummy cell for easier indexing
% This is where you tell Matlab what words/expressions you are looking for
A = cellfun(#isempty,regexp(cc{k},'(\w*hello|hello\w*|earth|water)','match'));
DummyCell(~A) = []; % Remove the cells containing the strings/words of interest
FinalCell{k} = DummyCell;
end
Then you're good to go. Hope that helps!
The closest thing possible I found is:
clear all
cc{1} = {'str_row1col1', 'str_row1col2' };
cc{2} = {'str_row2col1', 'bighello', 'str_row1col3' };
cc{3} = {'str_row3col1'};
cc{4} = {'str_row3col1', 'helloWorld'};
cc1 = [cc{:}];
cc1 = cc1(~strcmp('bighello',cc1));
This reorganize your array into a one dimensional array and it cannot match regular expression, but only whole words.
For a better job I am afraid you have to use for loops.
Using a combination of this question and this Mathworks help thing on comma sep. lists I came up with this ugly way to make my formatting arguments a little prettier:
formatting{1,1} = 'color'; formatting{2,1} = 'black';
formatting{1,2} = 'fontweight'; formatting{2,2} = 'bold';
formatting{1,3} = 'fontsize'; formatting{2,3} = 24;
xlabel('Distance', formatting{:});
But it's still kinda ugly...is there a way to unpack a structure into a bunch of arguments a la a Python dictionary to **kwargs?
For instance, if I had the (IMHO) cleaner structure:
formatting = struct()
formatting.color = 'black';
formatting.fontweight = 'bold';
formatting.fontsize = 24;
Can I just pass that in somehow? If I try directly (xlabel('blah', formatting), or formatting{:}, it craps out saying "Wrong number of arguments".
You are very close. Just switch to a 1-D cell array.
formatting = {'Color', 'Red', 'LineWidth', 10};
figure
plot(rand(1,10), formatting{:})
If you really want to use a struct for formatting arguments, you can unpack it to a cell array and use it like above.
formattingStruct = struct();
formattingStruct.color = 'black';
formattingStruct.fontweight = 'bold';
formattingStruct.fontsize = 24;
fn = fieldnames(formattingStruct);
formattingCell = {};
for i = 1:length(fn)
formattingCell = {formattingCell{:}, fn{i}, formattingStruct.(fn{i})};
end
plot(rand(1,10), formatting{:})
It's probably a good idea to do the struct unpacking a separate little function so you can reuse it easily.
You can convert your structure to cell array with this function:
function c = struct2opt(s)
fname = fieldnames(s);
fval = struct2cell(s);
c = [fname, fval]';
c = c(:);
Then
formatting = struct2opt(formattingStructure);
xlabel('Distance', formatting{:});
Using Matlab, write a function called tripFlip that takes in one string and switches each even-indexed charactar with the odd-indexed character immediately preceding it. Use iteration. Example: tripFlip('orange') ->'ronaeg'
I assume this is homework, so I won't give a complete answer. You can use double to convert a string to an array, and char to go back, if working with arrays makes the problem any easier. Otherwise, strings seem to work just like arrays in terms of indexing: s(1) gets the first character, length(s) gets the length, etc.
I agree its a homework question, and posting it here will only bite you back in the long run. But here goes:
a = 'orange';
b = '';
b(2:2:length(a))= a(1:2:end);
b(1:2:length(a))= a(2:2:end);
disp(b)
In one line:
>> input = 'orange';
>> output = input(reshape([2:2:end;1:2:end],1,[]))
output =
ronaeg
It's not a function and doesn't use iteration, but it's how you'd solve this if you were to learn Matlab.
Something like this should do the trick, perhaps you want to make it a bit more robust.
function b = TripFlip(a)
a = 'orange';
b = '';
for i = 2:2:length(a)
b=[b a(i) a(i-1)]
end