diff --git a/README.md b/README.md
index 7221a51805b3b3195eddf1b6cb196f5aa49ba1e5..69618325c07d41916cdd5f914e55b3f3f59561f6 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-# Popsimul
+# PopSimul
 
 ## Description
 
@@ -17,10 +17,10 @@ You can see all parameters by running this command
 | Short  | Long | Description | Default value |
 |---|---|---|---|  
 | -o  | --output | Name for the 3 generated files :  [output].vcf, [output]_errors.vcf, [output]_Breakpoints.csv | popsimul |
-| -n  | --nb_individuals | number of individuals | 10 |
-| -s  | --chr_size | chromosome size | 4000000|
+| -ni  | --nb_individuals | number of individuals | 10 |
+| -bp  | --chr_bp | chromosome size | 4000000|
 | -cM | --cM_size | size of genetic map | 180 |
-| -d  | --marker_density | marker density| 0.005 |
+| -nm  | --nb_markers | number of markers| 220000 |
 | -a  | --average_depth | average depth | 3 |
 | -m  | --max_depth | max depth | 10 |
 | -eA | --error_rate_A | error rate for A | 0.05 |
diff --git a/noisyplotype.py b/noisyplotype.py
index 92093badeeeadd99b4185ab568da5179e9f2629b..c8255c46301a46b633f23768fe4182f6afeeca16 100644
--- a/noisyplotype.py
+++ b/noisyplotype.py
@@ -196,16 +196,13 @@ def generate_chr_for_one_ind (mean_depth, markers_positions, conversion_factor,
     return segment, segment_error, breakpoints
 
 # Generate a list of individuals
-def generate_individuals (nb_individuals, chromosome_size, marker_density, mean_depth, conversion_factor, errA, errB):
+def generate_individuals (nb_individuals, chromosome_size, nb_markers, mean_depth, conversion_factor, errA, errB):
     matrix = []
     matrix_error = []
-
-    # Calculate the number of marker requiered
-    markers_nb = round(chromosome_size * marker_density)
     
     # Generate a sorted list of markers positions
     #markers_positions = sorted(random.sample(range(chromosome_size),size))
-    markers_positions = np.linspace(1, chromosome_size, markers_nb, dtype="int")
+    markers_positions = np.linspace(1, chromosome_size, nb_markers, dtype="int")
 
     with open(args.output + '_Breakpoints.csv', 'w') as breakpointFile:
         breakpointFile.write(",".join(["sample","average_bkp_position", "bkp_start_position", "bkp_stop_position", "transitionType"]) + "\n");
@@ -235,13 +232,13 @@ def generate_individuals (nb_individuals, chromosome_size, marker_density, mean_
 
 
 # define commandline arguments
-parser = argparse.ArgumentParser(description='Description of your program')
+parser = argparse.ArgumentParser(description='PopSimul')
 
 parser.add_argument('-o', '--output', help='Output files name', default="popsimul")
-parser.add_argument('-n', '--nb_individuals', help='Number of individuals', default=10)
-parser.add_argument('-s', '--chr_size', help='Chromosome size in bp', default=44000000)
+parser.add_argument('-ni', '--nb_individuals', help='Number of individuals', default=10)
+parser.add_argument('-bp', '--chr_bp', help='Chromosome size in bp', default=44000000)
 parser.add_argument('-cM', '--cM_size', help='Size of genetic map', default=180)
-parser.add_argument('-d', '--marker_density', help='Number of markers per bp', default=0.0058)
+parser.add_argument('-nm', '--nb_markers', help='Number of markers', default=220000)
 parser.add_argument('-a', '--average_depth', help='Depth average', default=3)
 parser.add_argument('-m', '--max_depth', help='Maximum possible depth', default=10)
 parser.add_argument('-eA', '--error_rate_A', help='Error rate', default=0.05)
@@ -251,12 +248,12 @@ args = parser.parse_args()
 
 # Set the parameters for the script
 nb_individuals = int(args.nb_individuals)
-chromosome_size = int(args.chr_size)
+chromosome_size = int(args.chr_bp)
 cMsize = int(args.cM_size)    ## Size of genetic map
 conversion_factor = chromosome_size/cMsize   ## Corresponds to a bpPercM conversion ! Needs to be fixed... Does not produce the correct division!
 #conversion_factor = 233000
 #marker_density = 255000/44000000
-marker_density = float(args.marker_density)
+nb_markers = int(args.nb_markers)
 mean_depth = float(args.average_depth)
 max_depth = float(args.max_depth) #TODO better estimate for max ?
 errA = float(args.error_rate_A)
@@ -264,9 +261,9 @@ errB = float(args.error_rate_B)
 
 print("-----USED PARAMETERS-----")
 print("nb_individuals =",str(nb_individuals))
-print("chromosome_size =",str(chromosome_size))
+print("chr_bp =",str(chromosome_size))
 print("cMsize =",str(cMsize))
-print("marker_density =",str(nb_individuals))
+print("nb_markers =",str(nb_markers))
 print("average_depth =",str(mean_depth))
 print("max_depth =",str(max_depth))
 print("error_rate_A =",str(errA))
@@ -274,7 +271,7 @@ print("error_rate_B =",str(errB))
 print("------------------------")
 
 ## Generate the pop and associate the results to the matrixes with and without errors
-pop = generate_individuals(nb_individuals, chromosome_size, marker_density, mean_depth, conversion_factor, errA, errB)
+pop = generate_individuals(nb_individuals, chromosome_size, nb_markers, mean_depth, conversion_factor, errA, errB)
 matrix = pop[0]
 matrix_error = pop[1]
 markers_positions = pop[2]
@@ -333,4 +330,4 @@ with open(args.output + '_errors.vcf', 'w') as file:
         row.append("0/0:"+ str(round(mean_depth)) + ":" + str(round(mean_depth)) + ",0:.:.:.:.")
         row.append("1/1:"+ str(round(mean_depth)) + ":0," + str(round(mean_depth)) + ":.:.:.:.")
         file.write("\t".join(row) + "\n");
-    print("The file", args.output, "has been generated")
\ No newline at end of file
+    print("The files", args.output + ".vcf, " + args.output + "_errors.vcf and " + args.output + "_Breakpoint.csv" , "have been generated")
\ No newline at end of file