How to assign different value to a variable for different if statement

Question

I have a text file with 4 columns. I need to modify the file so that the first sequence of 1's in the 4th column remain 1, but all other values in the 4th column be changed to 0.

I have tried the following awk command with multiple if statements but the variable fat doesn't seem to be updating properly.

`cat sample_data.txt`

72  29  16  0   <br>
73  30  16  0   <br>
74  31  16  0   <br>
75  32  16  1   <br>
76  33  16  1   <br>
77  34  16  1   <br>
78  35  16  0   <br>
79  36  16  0   <br>
80  37  16  0   <br>
81  38  16  0   <br>
82  39  16  0   <br>
83  40  16  0   <br>
84  41  16  0   <br>
85  42  16  0.55    <br>
86  43  16  0.57    <br>
87  44  16  0.41    <br>
88  45  16  0.58    <br>
89  46  16  1   <br>
90  47  16  1   <br>
91  48  16  1   <br>
92  49  16  1   <br>
93  50  16  0.59    <br>
94  51  16  0.52    <br>
95  52  16  0.43    <br>


`awk -v fat=1 '{if($4<1 && fat=1) {print $1,$2,$3,0;} else if($4=1 && fat=1) {fat=2;print $1,$2,$3,1;} else if($4=1 && fat=2) {fat=2;print $1,$2,$3,1;} else if($4<1 && fat=2) {fat=3;print $1,$2,$3,0} else if($4<1 && fat=3) {fat=3;print $1,$2,$3,0;} else if($4=1 && fat=3) {fat=3;print $1,$2,$3,0;}}' sample_data.txt`

I want this output:

72  29  16  0   <br>
73  30  16  0   <br>
74  31  16  0   <br>
75  32  16  1   <br>
76  33  16  1   <br>
77  34  16  1   <br>
78  35  16  0   <br>
79  36  16  0   <br>
80  37  16  0   <br>
81  38  16  0   <br>
82  39  16  0   <br>
83  40  16  0   <br>
84  41  16  0   <br>
85  42  16  0   <br>
86  43  16  0   <br>
87  44  16  0   <br>
88  45  16  0   <br>
89  46  16  0   <br>
90  47  16  0   <br>
91  48  16  0   <br>
92  49  16  0   <br>
93  50  16  0   <br>
94  51  16  0   <br>
95  52  16  0   <br>

edit your question to format your code and sample input/output properly by simply indenting them by 4 spaces. The editors {} button will do it for you. — Ed Morton
– Ed Morton, Commented Apr 18, 2019 at 4:24

Ed Morton · Accepted Answer · 2019-04-18 05:22:02Z

2

wrt your code:

if($4<1 && fat=1)

fat=1 is an assignment, an equivalency test would be fat==1 (double equals) instead.

But anyway, here's how to do what you appear to want with a simple FSM:

$ awk '(state==0) && ($4==1){state=1} (state==1) && ($4!=1){state=2} state==2{$4=0} 1' file
72 29 16 0
73 30 16 0
74 31 16 0
75 32 16 1
76 33 16 1
77 34 16 1
78 35 16 0
79 36 16 0
80 37 16 0
81 38 16 0
82 39 16 0
83 40 16 0
84 41 16 0
85 42 16 0
86 43 16 0
87 44 16 0
88 45 16 0
89 46 16 0
90 47 16 0
91 48 16 0
92 49 16 0
93 50 16 0
94 51 16 0
95 52 16 0

edited Apr 18, 2019 at 5:22

answered Apr 18, 2019 at 4:28

Ed Morton

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2 Comments

Ben Allen Over a year ago

This seems to work fine! I think I understand most of it, but could you explain the the 1 at the end?

Ed Morton Over a year ago

It's a true condition and so it causes awk to perform it's default action which is to print the current record. It's just idiomatic shorthand for {print}.

user7712945 · Accepted Answer · 2019-04-24 13:51:13Z

0

tried on gnu awk:

awk -vf=1 '$4==1&&(f||s){f=0;s=1;$4=0;print;next} {s=0}1' sample_data.txt

answered Apr 24, 2019 at 13:51

user7712945

1 Comment

Popo Over a year ago

While this command may answer the question, providing additional context regarding why and/or how this code answers the question improves its long-term value.

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