slice

问题 This question already has answers here : Understanding slice notation (32 answers) Closed 6 years ago . The extended slice syntax in python has been explained to me as " a[n:m:k] returns every kth element from n to m ". This gives me a good idea what to expect when k is positive. But I'm lost on how to interpret a[n:m:k] for negative k. I know that a[::-1] reverses a, and that a[::-k] takes ever kth element of the reversed a. But how is this a generalization of the definition for k positive?

问题 Suppose I have 20 Columns in a data set and i want to use 19 as an input. and input columns are columns from 1:10 and 12: 20. and I want to use 11th column as an output. so how to give this kind of range using pandas? for example: Example Data Set consider above data it have 4 columns but i have to take input only 3 columns but those columns are b,d,e and i want to skip c column. Right now i m using input = dftrain.loc[:, :'e' ] which consider all 4 columns. 回答1: Option 1 np.r_ idx = np.r_[0

问题 This question already has answers here : Select rows in pandas MultiIndex DataFrame (2 answers) Closed 12 months ago . I have a multi-index dataframe that looks like uid tid text abc x t1 bcd y t2 uid and tid are the indexes. I have a list of uid s, and want to get the rows corresponding to the uids in that list, but keeping the 2nd level index values (tid). I want to do it without running any explicit loop. Is that possible? 回答1: Data: L = ['abc', 'bcd'] print (df) text uid tid abc x t1 abc1

问题 I am looking for a way to store information which struct a function should use. Each struct corresponds to certain database table. type Record struct { TableName string PrimaryKey string //XormStruct // how can I store User or Post here? XormStruct2 interface{} // see I have tried below XormStruct3 reflect.Type // see I have tried below } var posts []Post var ListOfTables [...]Record { {"User", "id", User}, //{"Post", "post_id", Post}, {"Post", "post_id", posts, reflect.TypeOf([]Post{})}, } /

问题 I'm inexperienced with MATLAB, so sorry for the newbie question: I've got a large vector (905350 elements) storing a whole bunch of data in it. I have the standard deviation and mean, and now I want to cut out all the data points that are above/below one standard deviation from the mean. I just have no clue how. From what I gather I have to make a double loop of some sort? It's like: mean-std < data i want < mean + std 回答1: If the data is in variable A , with the mean stored in meanA and the

问题 I'm inexperienced with MATLAB, so sorry for the newbie question: I've got a large vector (905350 elements) storing a whole bunch of data in it. I have the standard deviation and mean, and now I want to cut out all the data points that are above/below one standard deviation from the mean. I just have no clue how. From what I gather I have to make a double loop of some sort? It's like: mean-std < data i want < mean + std 回答1: If the data is in variable A , with the mean stored in meanA and the

问题 I have a sound signal, imported as a numpy array and I want to cut it into chunks of numpy arrays. However, I want the chunks to contain only elements above a threshold. For example: threshold = 3 signal = [1,2,6,7,8,1,1,2,5,6,7] should output two arrays vec1 = [6,7,8] vec2 = [5,6,7] Ok, the above are lists, but you get my point. Here is what I tried so far, but this just kills my RAM def slice_raw_audio(audio_signal, threshold=5000): signal_slice, chunks = [], [] for idx in range(0, audio

问题 This question already has answers here : Identify groups of continuous numbers in a list (13 answers) Closed 11 months ago . Ive got a list which actually hold indices for another list. Hence I want to pick out the consecutive numbers from this list index_list=[3,4,8,9,35,36,37] from which i want the output as [3:4], [8:9], [35:37] ---------------------MOTIVE:--------------------- I have another master list of words, which has 80 words. master_list=['was,'it','to,'go,'I'.........] Thus the

问题 According to the Python documentation on extended slices: If you have a mutable sequence such as a list or an array you can assign to or delete an extended slice, but there are some differences between assignment to extended and regular slices. Assignment to a regular slice can be used to change the length of the sequence: >>> a = range(3) >>> a [0, 1, 2] >>> a[1:3] = [4, 5, 6] >>> a [0, 4, 5, 6] Extended slices aren't this flexible. When assigning to an extended slice, the list on the right

问题 I am looking for a efficient way to check if a slice is a subset of another. I could simply iterate over them to check, but I feel there has to be a better way. E.g. {1, 2, 3} is a subset of {1, 2, 3, 4} {1, 2, 2} is NOT a subset of {1, 2, 3, 4} What is the best way to do this efficiently? Thanks! 回答1: I think the most common way to solve a subset problem is via a map. package main import "fmt" // subset returns true if the first array is completely // contained in the second array. There