这个是小弟手头的一组数据（经过简化）
第三列为数据类型，四五列为跨越长度，第九列为特征ID，其余不管

1、首先我想只留下表1第三列为A的行，把A1A2A3的列都去掉，变成表2那样
2、其次，比如以EF为出发点，我想提取出以四五列的长度为依据，向上200、向下200距离的特征ID。比如EF的跨度是301到400，要把它上面100-300的AB,CD的ID，下面400-600的GH，IJ的ID提取出来
3、再进一步，如果要从CD，IL出发，分别同时把CD上下的AB，EF和IL上下的GH，KL的ID提取出来
求问用R应该如何写出程序？ 谢谢各位

chr1	HAVANA	A	100	200	.	+	.	ID = AB
chr1	HAVANA	A1	100	120	.	+	.	ID = AB
chr1	HAVANA	A2	121	156	.	+	.	ID = AB
chr1	HAVANA	A3	157	200	.	+	.	ID = AB
chr1	HAVANA	A	201	300	.	+	.	ID = CD
chr1	HAVANA	A1	201	267	.	+	.	ID = CD
chr1	HAVANA	A2	268	289	.	+	.	ID = CD
chr1	HAVANA	A3	289	300	.	+	.	ID = CD
chr1	HAVANA	A	301	400	.	-	.	ID = EF
chr1	HAVANA	A1	301	345	.	-	.	ID = EF
chr1	HAVANA	A2	346	378	.	-	.	ID = EF
chr1	HAVANA	A3	378	400	.	-	.	ID = EF
chr1	HAVANA	A	401	500	.	-	.	ID = GH
chr1	HAVANA	A1	401	434	.	-	.	ID = GH
chr1	HAVANA	A2	434	477	.	-	.	ID = GH
chr1	HAVANA	A3	477	500	.	-	.	ID = GH
chr1	HAVANA	A	501	600	.	-	.	ID = IJ
chr1	HAVANA	A1	501	524	.	-	.	ID = IJ
chr1	HAVANA	A2	524	568	.	-	.	ID = IJ
chr1	HAVANA	A3	568	600	.	-	.	ID = IJ
chr1	HAVANA	A	601	700	.	-	.	ID = KL
chr1	HAVANA	A1	601	647	.	-	.	ID = KL
chr1	HAVANA	A2	647	700	.	-	.	ID = KL

表1

chr1	HAVANA	A	100	200	.	+	.	ID = AB
chr1	HAVANA	A	201	300	.	+	.	ID = CD
chr1	HAVANA	A	301	400	.	-	.	ID = EF
chr1	HAVANA	A	401	500	.	-	.	ID = GH
chr1	HAVANA	A	501	600	.	-	.	ID = IJ
chr1	HAVANA	A	601	700	.	-	.	ID = KL

表2