I want to call multiple functions on the elements of a list with QtConcurrent::mapped. How can I do that? One way would be to to create a composite function and pass that to mapped. However I imagine that might have some drawbacks if the individual pieces of work take different amounts of time.
Is there a way to chain multiple calls to mapped? I would like it to apply the second function on an element as soon as the first function is finished. It should not process all elements with the first function first before starting with the second.
I'm looking for something like:
QtConcurrent::blockingMapped(QtConcurrent::mapped(images, scale), rotate);
What I don't want:
QtConcurrent::blockingMapped(images, scale);
QtConcurrent::blockingMapped(images, rotate);
I know that while and if functions in R are not vectorised. while and if functions help us selectively work on some rows based on some condition. I also know that the apply function in R is used to apply over the columns and hence it operates on all rows of columns that we wish to put apply on. Can I use apply() along with user defined functions and/or with while/if loop to conditionally use it over some rows rather than all rows as apply function usually does.
Note :- This core issue here is to bypass the drawback on non-vectorization of while/if loops in R.
You can supply user defined functions to apply using an argument FUN = function(x) user_defined_function(x) {}. And apply is "vectorized" in sense that as argument it accept vectors, not scalars (but its implementation is heavily using for and if loops, type apply without arguments in your console). So for and apply are of the same perfomance.
However you can break the execution of user defined function throwing exception with stop and wrapping in tryCatch it is a non-recommended technique (it influences environements, call stacks, scopes etc., make debugging difficult and lead to errors which are difficult to identify).
Better to use for and if and very often it is the most easiest and effective way (to write a recursive function, taking in consideration that (tail) recursion is not really optimized for R, or fully refactor your algorithm quite difficult and time consuming).
I have a list of roots and I want to plot the real/imaginary parts. If s=allroots(), r=realpart() and i=imagpart(), all with makelist(). Since length(s) can get ...lengthy, is there a way to plot point by point and have them numbered? Actually, the numbering part is what concerns me most. I can simply use points(r,i) and get the job done, but I'd like to know their occurence before and after some sorting algorithms. It's not always necessary to plot all the points, I can plot up until some number, but I do have to be able to see their order of having been sorted out.
I have tried multiplot_mode but it doesn't work:
multiplot_mode(wxt)$
for i:1 thru length(s) do draw2d(points([r[i]],[i[i]]))$
multiplot_mode(none)$
All I get is a single point. Now, if this should work, using draw2d's label(["label",posx,posy]) is very handy, but can I somehow evaluate i in the for loop inside the ""?
Or, is there any other way to do it? With Octave? or Scilab? I'm on Linux, btw.
Just to be clear, here's what I currently do: (I can't post images, here's the link: i.stack.imgur.com/hNYZF.png )
...and here is the wxMaxima code:
ptest:sortd(pp2); length(ptest);
draw2d(proportional_axes=xy,xrange=[sort(realpart(s))[1]-0.1,sort(realpart(s))[length(s)]+0.1],
yrange=[sort(imagpart(s))[1]-0.1,sort(imagpart(s))[length(s)]+0.1],point_type=0,
label(["1",realpart(ptest[1]),imagpart(ptest[1])]),points([realpart(ptest[1])],[imagpart(ptest[1])]),
label(["2",realpart(ptest[2]),imagpart(ptest[2])]),points([realpart(ptest[2])],[imagpart(ptest[2])]),
label(["3",realpart(ptest[3]),imagpart(ptest[3])]),points([realpart(ptest[3])],[imagpart(ptest[3])]),
label(["4",realpart(ptest[4]),imagpart(ptest[4])]),points([realpart(ptest[4])],[imagpart(ptest[4])]),
label(["5",realpart(ptest[5]),imagpart(ptest[5])]),points([realpart(ptest[5])],[imagpart(ptest[5])]),
label(["6",realpart(ptest[6]),imagpart(ptest[6])]),points([realpart(ptest[6])],[imagpart(ptest[6])]),
label(["7",realpart(ptest[7]),imagpart(ptest[7])]),points([realpart(ptest[7])],[imagpart(ptest[7])]),
label(["8",realpart(ptest[8]),imagpart(ptest[8])]),points([realpart(ptest[8])],[imagpart(ptest[8])]),
label(["9",realpart(ptest[9]),imagpart(ptest[9])]),points([realpart(ptest[9])],[imagpart(ptest[9])]),
label(["10",realpart(ptest[10]),imagpart(ptest[10])]),points([realpart(ptest[10])],[imagpart(ptest[10])]),
label(["11",realpart(ptest[11]),imagpart(ptest[11])]),points([realpart(ptest[11])],[imagpart(ptest[11])]),
label(["12",realpart(ptest[12]),imagpart(ptest[12])]),points([realpart(ptest[12])],[imagpart(ptest[12])]),/*
label(["13",realpart(ptest[13]),imagpart(ptest[13])]),points([realpart(ptest[13])],[imagpart(ptest[13])]),
label(["14",realpart(ptest[14]),imagpart(ptest[14])]),points([realpart(ptest[14])],[imagpart(ptest[14])]),*/
color=red,point_type=circle,point_size=3,points_joined=false,points(realpart(pp2),imagpart(pp2)),points_joined=false,
color=black,key="",line_type=dots,nticks=50,polar(1,t,0,2*%pi) )$
This is for 14 zeroes, only. For higher orders it would be very painful.
I gather that the problem is that you want to automatically construct all the points([realpart(...), imagpart(...)]). My advice is to construct the list of points expressions via makelist, then append that list to any other plotting arguments, then apply the plotting function to the appended list. Something like:
my_labels_and_points :
apply (append,
makelist ([label ([sconcat (i), realpart (ptest[i]), imagpart (ptest[i])]),
points ([realpart (ptest[i])], [imagpart (ptest[i])])],
i, 1, length (ptest)));
all_plot_args : append ([proptional_axes=..., ...], my_labels_and_points, [color=..., key=..., ...]);
apply (draw2d, all_plot_args);
The general idea is to build up the list of plotting arguments and then apply the plotting function to that.
I'm trying to create a histogram of an image. I was thinking to first bubblesort the array of the pixels so every number is sorted from low to high.
Then its easier to count how many times a specific value of a pixels appears. And then later I can put it in a graph.
But it always gives an error then I don't understand.
I also want to make everything with the formula node instead of just blocks.
Visual:
http://i.stack.imgur.com/ZlmW2.png
Error:
http://i.stack.imgur.com/91TbS.png
In your code numbers is a scalar not an array.
Besides that the formula node does not maintain state, you'll need a feedback node to get history. Is there any reason why do you want to use the formula node instead of native LabVIEW code?
You need to remove the two nested LabVIEW for loops, you are iterating through your array inside the formula node so you don't need to do it with the loops.
A follow-up question from Graphite: sum all stats that match a pattern?:
Is there any Graphite magic to recursively descend node names? I now know that I can use patterns like so:
stats.timers.api.*.200.count
... but imagine that I have the following:
stats.timers.api.foo.bar.200.count
stats.timers.api.baz.200.count
I'd like to see both of those stats (and all others of arbitrary depth) on the same chart. I tried the following:
stats.timers.api.*.200.count
stats.timers.api.**.200.count
The former only shows me items like the 'baz' example above; the latter is an error.
Is there some other way to match metrics in a depth-insensitive manner?
A neater, single line version of dannyla's answer would be:
stats.timers.api.{*,*.*,*.*.*}.200.count
But the short answer to your question would no, there's no magic to recursively descend node names.
I know its not the 100% what you are after, however you can have multiple targets on the same graph.
You could just combine the below on to the same graph that will give you the results, however not the clean solution your after.
stats.timers.api.*.200.count
stats.timers.api.*.*.200.count
stats.timers.api.*.*.*.200.count