##### Checking the elements of a matrix with an elements of a list
 Checking the elements of a matrix with an elements of a list juniorcoder Silly Frenchman Posts: 30 Threads: 12 Joined: Jul 2017 Reputation: Sep-16-2018, 02:44 PM Hello folks, I need a small help , it is very easy question but since I am beginner I stucked a bit. I have a matrix like that : C=[[1 2 3 4 ] [7 8 9 10] [12 13 14 15] [5 7 7 6]] I need to check all the elements of third line of matrix [12 13 14 15]: If first element is > b: do this with the same fashion from first to fourth which is 15 , I have to check. I could not select specifically third line of matrix to check the elements ? How can I do that ? Thank you Reply gruntfutuk Spam, spam, eggs, and spam Posts: 229 Threads: 2 Joined: Sep 2017 Reputation: Sep-16-2018, 02:55 PM (This post was last modified: Sep-16-2018, 02:55 PM by gruntfutuk.) Try this, should help you figure it out: ```C=[[1, 2, 3, 4 ], [7, 8, 9, 10], [12, 13, 14, 15], [5, 7, 7, 6]] for row in C: print(row) for element in row: print(element) print(C[3]) print(C[3][2])``` I am trying to help you, really, even if it doesn't always seem that way Reply juniorcoder Silly Frenchman Posts: 30 Threads: 12 Joined: Jul 2017 Reputation: Sep-16-2018, 03:16 PM (This post was last modified: Sep-16-2018, 03:17 PM by juniorcoder.) Hello thank you , but how can I read the third line of matrix one by one 12,13,14,15? what I am trying to do: if 12>a: do this if 13>b: do this etc Reply gruntfutuk Spam, spam, eggs, and spam Posts: 229 Threads: 2 Joined: Sep 2017 Reputation: Sep-16-2018, 09:05 PM That is shown in the code I shared. You need to try it and experiment. I am trying to help you, really, even if it doesn't always seem that way Reply juniorcoder Silly Frenchman Posts: 30 Threads: 12 Joined: Jul 2017 Reputation: Sep-17-2018, 11:03 AM Hello, I have an easy question. I have an matrix like C=[[1 2 3] [4 5 6] [7 8 9] and I have a list L=[5 10 5] I need to check if the elements of first line is less than 5 (L[0]), if the elements of second line is less than 10(L[1]) and if the elements of last line is less than 10(L[2]) And I need the combine this check with other condition : Let's say if a>b and "the controls above" How can I write it ? Thank you so much Reply Larz60+ aetate et sapientia Posts: 10,863 Threads: 410 Joined: Sep 2016 Reputation: Sep-17-2018, 12:08 PM (This post was last modified: Sep-17-2018, 12:08 PM by Larz60+.) how to you think it should be written? Give it a go. Reply juniorcoder Silly Frenchman Posts: 30 Threads: 12 Joined: Jul 2017 Reputation: Sep-17-2018, 12:10 PM (This post was last modified: Sep-17-2018, 12:15 PM by juniorcoder.) I had thought : if (a<=b and all(C[i][n]<=L[i]) for i in range(T)for n in range(N)): Do this but it did not work Reply Larz60+ aetate et sapientia Posts: 10,863 Threads: 410 Joined: Sep 2016 Reputation: Sep-17-2018, 12:35 PM ```>>> c=[[1, 2, 3], [4, 5, 6], [7, 8, 9]] >>> sum(c[0]) < 5 and (sum(c[1]) < 10 and sum(c[2]) < 10) False >>> ``` Reply juniorcoder Silly Frenchman Posts: 30 Threads: 12 Joined: Jul 2017 Reputation: Sep-17-2018, 12:42 PM But we do not know the content of list L=[5 10 5] I just gave an example like that: I should use the index of L to for the right hand side of inequlaity. and the other question how will I build the if statement with the first condition ? Than you Reply volcano63 Verb Conjugator Posts: 566 Threads: 10 Joined: Apr 2017 Reputation: Sep-17-2018, 01:09 PM Numpy arrays are intended to be used as objects - looping is wasteful and inefficient. This is how you can compare by rows and by columns ``````Output:In [89]: table = numpy.array(range(1, 10)).reshape(3, 3) In [90]: table Out[90]: array([[1, 2, 3], [4, 5, 6], [7, 8, 9]]) In [91]: compare_to = numpy.array([2, 5, 6]) In [92]: compare_to Out[92]: array([2, 5, 6]) In [93]: # Compare by columns In [94]: table < compare_to Out[94]: array([[ True, True, True], [False, False, False], [False, False, False]]) In [95]: # Compare by rows In [96]: table < compare_to.reshape(3, 1) Out[96]: array([[ True, False, False], [ True, False, False], [False, False, False]])```````numpy` is a complex package - going into it without learning Python is a bad idea, and using it without learning is an exercise in futility Test everything in a Python shell (iPython, Azure Notebook, etc.)Someone gave you an advice you liked? Test it - maybe the advice was actually bad. Someone gave you an advice you think is bad? Test it before arguing - maybe it was good. You posted a claim that something you did not test works? Be prepared to eat your hat. Reply

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