Champ de vecteur invisible?

Bonjour,

je cherche à représenter un champ de vecteur sur une grille 60*60 (le problème est que plus tard, cette grille pourra être 1000*1000)...

j'ai donc deux vecteurs de taille 60, deux matrices de taille 60, et je fais

champ(x,y,VX,VY)

seul problème : on voit rien sur le graphe

en zoomant, on arrive à voir des petites fleches à partir d'une résolution de 10^-15 et après ça on voit plus rien du tout
seul problème : mes matrices VX et VY ont des coefficients qui ont une taille de l'ordre de 10^-2

je me suis dit que c'était la taille de la grille qui est trop grande alors je me suis contenté de ploter sur 9 points seulement, et là ça marche nickel. A 100 points (10*10) on y voit moins mais ça va encore et à 60*60 on voit plus rien du tout...

aidez moi svp parce que je sais pas quoi faire...

le poulpe

ps : mon source :

 N=60;
 x=[1:N];
 y=[1:N];
 fx = [1:N];
 fy=[1:N];
 VX=zeros(N);
 VY=zeros(N);
 x(            1 ) =     96.36916172181394     
 y(            1 ) =    -62.57371840658895     
 fx(            1 ) =   -2.8756358296959661E-003
 fy(            1 ) =   -0.1184229403780709     
 x(            2 ) =     86.75963357204049     
 y(            2 ) =    -62.57383220541413     
 fx(            2 ) =   -4.6752825310250046E-003
 fy(            2 ) =   -0.1170792596534622     
 x(            3 ) =     77.15009091885717     
 y(            3 ) =    -62.57394471317548     
 fx(            3 ) =   -6.7199212462583091E-003
 fy(            3 ) =   -0.1132926535595782     
 x(            4 ) =     62.73578655011695     
 y(            4 ) =    -62.57410801654486     
 fx(            4 ) =   -1.0236064799755695E-002
 fy(            4 ) =   -0.1062392891288863     
 x(            5 ) =     48.32147079065804     
 y(            5 ) =    -62.57426115305406     
 fx(            5 ) =   -1.4551968379237223E-002
 fy(            5 ) =   -9.2491382306089345E-002
 x(            6 ) =     24.29761002668698     
 y(            6 ) =    -62.57448335273975     
 fx(            6 ) =   -1.8081449641613290E-002
 fy(            6 ) =   -7.1100837719897517E-002
 x(            7 ) =    0.2737419087852352     
 y(            7 ) =    -62.57465416414575     
 fx(            7 ) =   -1.7754401565980515E-002
 fy(            7 ) =   -4.7696747232926953E-002
 x(            8 ) =    -23.75012542342194     
 y(            8 ) =    -62.57476874997508     
 fx(            8 ) =   -1.3608833301987033E-002
 fy(            8 ) =   -2.6251768436961524E-002
 x(            9 ) =    -47.77398392162172     
 y(            9 ) =    -62.57483181676628     
 fx(            9 ) =   -8.7501532398164272E-003
 fy(            9 ) =   -1.2434515154164105E-002
 x(           10 ) =    -62.18829753924298     
 y(           10 ) =    -62.57484974025071     
 fx(           10 ) =   -4.8746360916993581E-003
 fy(           10 ) =   -5.3110421924591261E-003
 x(           11 ) =    -76.60259924813481     
 y(           11 ) =    -62.57485739574343     
 fx(           11 ) =   -2.4556320131523535E-003
 fy(           11 ) =   -1.4709455408614942E-003
 x(           12 ) =    -86.21213976833648     
 y(           12 ) =    -62.57485880925416     
 fx(           12 ) =   -4.3578631448326632E-004
 fy(           12 ) =   -6.1334904353711281E-005
 x(           13 ) =     95.90181907387043     
 y(           13 ) =    -35.92999599716627     
 fx(           13 ) =    1.7411063527106307E-003
 fy(           13 ) =   -4.5346240846410972E-002
 x(           14 ) =     86.29229536056710     
 y(           14 ) =    -35.93003957275153     
 fx(           14 ) =   -1.4910016943758819E-004
 fy(           14 ) =   -4.4851177174266496E-002
 x(           15 ) =     76.68275705683600     
 y(           15 ) =    -35.93008267266139     
 fx(           15 ) =   -2.3545439835288562E-003
 fy(           15 ) =   -4.3488070960954014E-002
 x(           16 ) =     62.26845898047920     
 y(           16 ) =    -35.93014535764839     
 fx(           16 ) =   -6.0110240992798936E-003
 fy(           16 ) =   -4.0831154711611348E-002
 x(           17 ) =     47.85414931112113     
 y(           17 ) =    -35.93020421290383     
 fx(           17 ) =   -1.0530429750360781E-002
 fy(           17 ) =   -3.5549721278481793E-002
 x(           18 ) =     23.83029820842441     
 y(           18 ) =    -35.93028961693497     
 fx(           18 ) =   -1.4358243206515908E-002
 fy(           18 ) =   -2.7222706116391524E-002
 x(           19 ) =   -0.1935609649114625     
 y(           19 ) =    -35.93035501628687     
 fx(           19 ) =   -1.4555997131537879E-002
 fy(           19 ) =   -1.8111086880074345E-002
 x(           20 ) =    -24.21742061332790     
 y(           20 ) =    -35.93039852604447     
 fx(           20 ) =   -1.1120061950350646E-002
 fy(           20 ) =   -9.7936937829908657E-003
 x(           21 ) =    -48.24127313254674     
 y(           21 ) =    -35.93042205424381     
 fx(           21 ) =   -6.9181847375148209E-003
 fy(           21 ) =   -4.5266075645824704E-003
 x(           22 ) =    -62.65558410951346     
 y(           22 ) =    -35.93042857903221     
 fx(           22 ) =   -3.4960582324856659E-003
 fy(           22 ) =   -1.8793892708653369E-003
 x(           23 ) =    -77.06988383128254     
 y(           23 ) =    -35.93043128803929     
 fx(           23 ) =   -1.4938144413463306E-003
 fy(           23 ) =   -5.2362413600357514E-004
 x(           24 ) =    -86.67942342722195     
 y(           24 ) =    -35.93043179121790     
 fx(           24 ) =    2.4089791259029880E-004
 fy(           24 ) =   -2.3970304196731450E-005
 x(           25 ) =     96.21988659984909     
 y(           25 ) =   -5.1406776249732349E-015
 fx(           25 ) =   -8.7352498849213589E-004
 fy(           25 ) =   -2.1403930686298731E-017
 x(           26 ) =     86.61036037400913     
 y(           26 ) =   -5.1406981931347648E-015
 fx(           26 ) =   -2.9026990687270882E-003
 fy(           26 ) =   -2.5992024622687385E-017
 x(           27 ) =     77.00081942419666     
 y(           27 ) =   -5.1407231702700128E-015
 fx(           27 ) =   -5.3945203198964009E-003
 fy(           27 ) =   -3.8718124836986124E-017
 x(           28 ) =     62.58651696592839     
 y(           28 ) =   -5.1407789797161080E-015
 fx(           28 ) =   -9.3947593104530824E-003
 fy(           28 ) =   -4.1752013624750485E-017
 x(           29 ) =     48.17220241915253     
 y(           29 ) =   -5.1408391623253027E-015
 fx(           29 ) =   -1.4294148051703814E-002
 fy(           29 ) =   -3.2708410827689775E-017
 x(           30 ) =     24.14834227456453     
 y(           30 ) =   -5.1409177404417096E-015
 fx(           30 ) =   -1.8258869416968082E-002
 fy(           30 ) =    8.5373171941654987E-018
 x(           31 ) =    0.1244737304326386     
 y(           31 ) =   -5.1408972305405591E-015
 fx(           31 ) =   -1.8163898559578229E-002
 fy(           31 ) =    2.3045111037827202E-017
 x(           32 ) =    -23.89939458554294     
 y(           32 ) =   -5.1408418673698302E-015
 fx(           32 ) =   -1.3972871916848817E-002
 fy(           32 ) =    2.4783526566137153E-017
 x(           33 ) =    -47.92325395830274     
 y(           33 ) =   -5.1407823278573255E-015
 fx(           33 ) =   -8.9342167775612324E-003
 fy(           33 ) =    2.0611122052126032E-017
 x(           34 ) =    -62.33756784123873     
 y(           34 ) =   -5.1407526183655947E-015
 fx(           34 ) =   -4.7824073062656680E-003
 fy(           34 ) =    3.7324781956762549E-018
 x(           35 ) =    -76.75186941718927     
 y(           35 ) =   -5.1407472382615338E-015
 fx(           35 ) =   -2.2255081330513349E-003
 fy(           35 ) =    1.1342165670510863E-018
 x(           36 ) =    -86.36140971625252     
 y(           36 ) =   -5.1407461483317955E-015
 fx(           36 ) =   -7.6010675911675207E-005
 fy(           36 ) =    3.6647193981689748E-018
 x(           37 ) =     95.90181907387046     
 y(           37 ) =     35.92999599716627     
 fx(           37 ) =    1.7411063527106307E-003
 fy(           37 ) =    4.5346240846410972E-002
 x(           38 ) =     86.29229536056712     
 y(           38 ) =     35.93003957275153     
 fx(           38 ) =   -1.4910016943758819E-004
 fy(           38 ) =    4.4851177166872355E-002
 x(           39 ) =     76.68275705683602     
 y(           39 ) =     35.93008267266138     
 fx(           39 ) =   -2.3545439908048138E-003
 fy(           39 ) =    4.3488070956024576E-002
 x(           40 ) =     62.26845898047922     
 y(           40 ) =     35.93014535764837     
 fx(           40 ) =   -6.0110241047368618E-003
 fy(           40 ) =    4.0831154721470204E-002
 x(           41 ) =     47.85414931112114     
 y(           41 ) =     35.93020421290382     
 fx(           41 ) =   -1.0530429748541792E-002
 fy(           41 ) =    3.5549721275524131E-002
 x(           42 ) =     23.83029820842443     
 y(           42 ) =     35.93028961693496     
 fx(           42 ) =   -1.4358243206515908E-002
 fy(           42 ) =    2.7222706116391524E-002
 x(           43 ) =   -0.1935609649114395     
 y(           43 ) =     35.93035501628686     
 fx(           43 ) =   -1.4555997131537879E-002
 fy(           43 ) =    1.8111086880074345E-002
 x(           44 ) =    -24.21742061332788     
 y(           44 ) =     35.93039852604446     
 fx(           44 ) =   -1.1120061950350646E-002
 fy(           44 ) =    9.7936937859485224E-003
 x(           45 ) =    -48.24127313254672     
 y(           45 ) =     35.93042205424381     
 fx(           45 ) =   -6.9181847375148209E-003
 fy(           45 ) =    4.5266075596530411E-003
 x(           46 ) =    -62.65558410951344     
 y(           46 ) =     35.93042857903220     
 fx(           46 ) =   -3.4960582379426342E-003
 fy(           46 ) =    1.8793892708653369E-003
 x(           47 ) =    -77.06988383128252     
 y(           47 ) =     35.93043128803927     
 fx(           47 ) =   -1.4938144413463306E-003
 fy(           47 ) =    5.2362413600357514E-004
 x(           48 ) =    -86.67942342722193     
 y(           48 ) =     35.93043179121788     
 fx(           48 ) =    2.4089791259029880E-004
 fy(           48 ) =    2.3970311590881598E-005
 x(           49 ) =     96.36916172181397     
 y(           49 ) =     62.57371840658895     
 fx(           49 ) =   -2.8756358296959661E-003
 fy(           49 ) =    0.1184229403854651     
 x(           50 ) =     86.75963357204051     
 y(           50 ) =     62.57383220541415     
 fx(           50 ) =   -4.6752825164730893E-003
 fy(           50 ) =    0.1170792596460680     
 x(           51 ) =     77.15009091885722     
 y(           51 ) =     62.57394471317549     
 fx(           51 ) =   -6.7199212553532561E-003
 fy(           51 ) =    0.1132926535595782     
 x(           52 ) =     62.73578655011698     
 y(           52 ) =     62.57410801654486     
 fx(           52 ) =   -1.0236064799755695E-002
 fy(           52 ) =    0.1062392891338158     
 x(           53 ) =     48.32147079065807     
 y(           53 ) =     62.57426115305407     
 fx(           53 ) =   -1.4551968379237223E-002
 fy(           53 ) =    9.2491382306089345E-002
 x(           54 ) =     24.29761002668701     
 y(           54 ) =     62.57448335273977     
 fx(           54 ) =   -1.8081449643432279E-002
 fy(           54 ) =    7.1100837719897517E-002
 x(           55 ) =    0.2737419087852619     
 y(           55 ) =     62.57465416414576     
 fx(           55 ) =   -1.7754401565980515E-002
 fy(           55 ) =    4.7696747232926953E-002
 x(           56 ) =    -23.75012542342191     
 y(           56 ) =     62.57476874997509     
 fx(           56 ) =   -1.3608833298349055E-002
 fy(           56 ) =    2.6251768431046207E-002
 x(           57 ) =    -47.77398392162169     
 y(           57 ) =     62.57483181676628     
 fx(           57 ) =   -8.7501532398164272E-003
 fy(           57 ) =    1.2434515159093532E-002
 x(           58 ) =    -62.18829753924295     
 y(           58 ) =     62.57484974025071     
 fx(           58 ) =   -4.8746360971563263E-003
 fy(           58 ) =    5.3110421924591261E-003
 x(           59 ) =    -76.60259924813478     
 y(           59 ) =     62.57485739574344     
 fx(           59 ) =   -2.4556320131523535E-003
 fy(           59 ) =    1.4709455482556347E-003
 x(           60 ) =    -86.21213976833646     
 y(           60 ) =     62.57485880925417     
 fx(           60 ) =   -4.3578633085417096E-004
 fy(           60 ) =    6.1334896959561129E-005
 for i=1:60, for j=1:60, VX(i,j) = fx(i), end, end;
 for i=1:60, for j=1:60, VY(i,j) = fx(i), end, end;
 champ(x,y,100*VX,100*VY);

(les parenthèses bizarre c'est parce que fichier est fabriqué par des write fortran...)